Blackfin arch: fix bug NOR Flash MTD mount fail

Config EBIU flash mode properly. EBIU_MODE EBIU_FCTL
EBIU_MBSCTL register should be configurd to Flash
mode.

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>

diff --git a/arch/blackfin/mach-bf548/head.S b/arch/blackfin/mach-bf548/head.S
index 3071c24..74b34c7 100644
--- a/arch/blackfin/mach-bf548/head.S
+++ b/arch/blackfin/mach-bf548/head.S
@@ -158,6 +158,27 @@
 	w[p2] = r0;
 	ssync;
 
+	p2.h = hi(EBIU_MBSCTL);
+	p2.l = lo(EBIU_MBSCTL);
+	r0.h = hi(CONFIG_EBIU_MBSCTLVAL);
+	r0.l = lo(CONFIG_EBIU_MBSCTLVAL);
+	[p2] = r0;
+	ssync;
+
+	p2.h = hi(EBIU_MODE);
+	p2.l = lo(EBIU_MODE);
+	r0.h = hi(CONFIG_EBIU_MODEVAL);
+	r0.l = lo(CONFIG_EBIU_MODEVAL);
+	[p2] = r0;
+	ssync;
+
+	p2.h = hi(EBIU_FCTL);
+	p2.l = lo(EBIU_FCTL);
+	r0.h = hi(CONFIG_EBIU_FCTLVAL);
+	r0.l = lo(CONFIG_EBIU_FCTLVAL);
+	[p2] = r0;
+	ssync;
+
 	/* This section keeps the processor in supervisor mode
 	 * during kernel boot.  Switches to user mode at end of boot.
 	 * See page 3-9 of Hardware Reference manual for documentation.