feat(bl_common): import BL_NOBITS_{BASE,END} when defined

If SEPARATE_NOBITS_REGION is enabled, the platform may need to map
memory specifically for that region. Import the symbols from the linker
script to allow the platform to do so.
Signed-off-by: Samuel Holland <samuel@sholland.org>
Change-Id: Iaec4dee94a6735b22f58f7b61f18d53e7bc6ca8d

include/common/bl_common.h

@@ -106,6 +106,10 @@ IMPORT_SYM(uintptr_t, __RODATA_END__,		BL_RO_DATA_END);
 IMPORT_SYM(uintptr_t, __RO_START__,		BL_CODE_BASE);
 IMPORT_SYM(uintptr_t, __RO_END__,		BL_CODE_END);
 #endif
+#if SEPARATE_NOBITS_REGION
+IMPORT_SYM(uintptr_t, __NOBITS_START__,		BL_NOBITS_BASE);
+IMPORT_SYM(uintptr_t, __NOBITS_END__,		BL_NOBITS_END);
+#endif
 IMPORT_SYM(uintptr_t, __RW_END__,		BL_END);
 
 #if defined(IMAGE_BL1)