Add ap6256 wfi/bt firmware

 Some version info from the binary:

 BCM4345C5 - Ampak_CL1.5 UART 37.4 MHz BT 5.0 [Baseline: 0021]

 fw_bcm43456c5*.bin - version: 7.45.96.0 CRC: 1d0e37c2 Date:
 Fri 2017-06-16 12:39:23 CST Ucode Ver: 1043.2070 FWID: 01-1813af84

 nvram_ap6256.txt - AP6256_NVRAM_V1.1_08252017

 Tested on ROCK Pi 4 model B.
Signed-off-by: brian <brian@vamrs.com>

rkwifi/nvram_ap6256.txt

+#AP6256_NVRAM_V1.1_08252017
+# Cloned from bcm94345wlpagb_p2xx.txt 
+NVRAMRev=$Rev: 498373 $
+sromrev=11
+vendid=0x14e4
+devid=0x43ab
+manfid=0x2d0
+prodid=0x06e4
+macaddr=00:90:4c:c5:12:38
+nocrc=1
+boardtype=0x6e4
+boardrev=0x1304
+xtalfreq=37400
+#boardflags: 5GHz eTR switch by default
+#            2.4GHz eTR switch by default
+#            bit1 for btcoex
+boardflags=0x00480201
+boardflags2=0x40800000
+boardflags3=0x48200100
+#phycal_tempdelta=15
+rxchain=1
+txchain=1
+aa2g=1
+aa5g=1
+tssipos5g=1
+tssipos2g=1
+femctrl=0
+AvVmid_c0=0,157,1,126,1,126,1,126,1,126
+pa2ga0=-164,5427,-623
+pa2ga1=-165,3699,-515
+#pa5ga0=-146,5304,-612,-140,5341,-613,-166,5326,-633,-154,5272,-621
+#pa5ga0=-134,5385,-609,-132,5359,-605,-154,5360,-621,-140,5288,-604
+pa5ga0=-127,5380,-603,-130,5395,-608,-148,5369,-622,-147,5222,-608
+pa5ga1=-161,3544,-499,-166,3543,-497,-169,3569,-497,-171,3598,-498
+itrsw=1
+pdoffset2g40ma0=10
+pdoffset40ma0=0xaaaa
+pdoffset80ma0=0xaaaa
+extpagain5g=2
+extpagain2g=2
+tworangetssi2g=0
+tworangetssi5g=0
+# LTECX flags
+# WCI2
+ltecxmux=0
+ltecxpadnum=0x0504
+ltecxfnsel=0x22
+ltecxgcigpio=0x32
+
+pacalshift5g=0,0,3
+
+maxp2ga0=70
+cckbw202gpo=0x1000
+cckbw20ul2gpo=0x1000
+ofdmlrbw202gpo=0x0033
+dot11agofdmhrbw202gpo=0x2222
+mcsbw202gpo=0x99333322
+
+cckdigfilttype=5
+
+#maxp5ga0=82,82,82,82
+#mcsbw205glpo=0x99555000
+#mcsbw205gmpo=0x99555000
+#mcsbw205ghpo=0x99555000
+#mcsbw405glpo=0x99555000
+#mcsbw405gmpo=0x99555000
+#mcsbw405ghpo=0x99555000
+#mcsbw805glpo=0x99555000
+#mcsbw805gmpo=0x99555000
+#mcsbw805ghpo=0x99555000
+
+maxp5ga0=73,74,73,73     
+mcsbw205glpo=0x8a875444
+mcsbw205gmpo=0x8a875444
+mcsbw205ghpo=0x8a875444
+
+mcsbw405glpo=0xda844333
+mcsbw405gmpo=0xdb844333
+mcsbw405ghpo=0xda844333
+
+mcsbw805glpo=0xdb555444
+mcsbw805gmpo=0xda555444
+mcsbw805ghpo=0xda555444
+
+
+swctrlmap_2g=0x00040004,0x00020002,0x00040004,0x010a02,0x1ff
+swctrlmap_5g=0x00100010,0x00200020,0x00200020,0x010a02,0x2f4
+swctrlmapext_5g=0x00000000,0x00000000,0x00000000,0x000000,0x3
+swctrlmapext_2g=0x00000000,0x00000000,0x00000000,0x000000,0x3
+
+vcodivmode=1
+deadman_to=481500000
+ed_thresh2g=-54
+ed_thresh5g=-54
+eu_edthresh2g=-54
+eu_edthresh5g=-54
+
+
+muxenab=0x10