[ARM] 3967/1: xsc3: make branch predication configurable on xsc3

Remove BTB_ENABLE from proc-xsc3.S

On some early revisions of xsc3 enabling the branch target buffer can cause
crashes, see erratum #42.

Cc: Lennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mm/Kconfig

@@ -580,7 +580,7 @@ config CPU_CACHE_ROUND_ROBIN
 
 config CPU_BPREDICT_DISABLE
 	bool "Disable branch prediction"
-	depends on CPU_ARM1020 || CPU_V6
+	depends on CPU_ARM1020 || CPU_V6 || CPU_XSC3
 	help
 	  Say Y here to disable branch prediction.  If unsure, say N.
 

arch/arm/mm/proc-xsc3.S

@@ -56,11 +56,6 @@
  */
 #define L2_CACHE_ENABLE	1
 
-/*
- * Enable the Branch Target Buffer (can cause crashes, see erratum #42.)
- */
-#define BTB_ENABLE	0
-
 /*
  * This macro is used to wait for a CP15 write and is needed
  * when we have to ensure that the last operation to the co-pro
@@ -434,9 +429,7 @@ __xsc3_setup:
 	mrc	p15, 0, r0, c1, c0, 0		@ get control register
 	bic	r0, r0, r5			@ .... .... .... ..A.
 	orr	r0, r0, r6			@ .... .... .... .C.M
-#if BTB_ENABLE
 	orr	r0, r0, #0x00000800		@ ..VI Z..S .... ....
-#endif
 #if L2_CACHE_ENABLE
 	orr 	r0, r0, #0x04000000		@ L2 enable
 #endif