fix(plat/allwinner): delay after enabling CPU power

Adds a 1us delay after enabling power to a CPU core, to prevent
inrush-caused CPU crash before it's up.

Change-Id: I8f4c1b0dc0d1d976b31ddc30efe7a77a1619b1b3
Signed-off-by: Icenowy Zheng <icenowy@sipeed.com>

plat/allwinner/common/sunxi_cpu_ops.c

@@ -42,6 +42,7 @@ static void sunxi_cpu_enable_power(unsigned int cluster, unsigned int core)
 	mmio_write_32(SUNXI_CPU_POWER_CLAMP_REG(cluster, core), 0xe0);
 	mmio_write_32(SUNXI_CPU_POWER_CLAMP_REG(cluster, core), 0x80);
 	mmio_write_32(SUNXI_CPU_POWER_CLAMP_REG(cluster, core), 0x00);
+	udelay(1);
 }
 
 /* We can't turn ourself off like this, but it works for other cores. */