ARM: 8942/1: Revert "8857/1: efi: enable CP15 DMB instructions before cleaning the cache"

This reverts commit e17b1af9, which is
no longer necessary now that the v7 specific routines take care not to
issue CP15 barrier instructions before they are enabled in SCTLR.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

arch/arm/boot/compressed/head.S

@@ -1460,21 +1460,7 @@ ENTRY(efi_stub_entry)
 
 		@ Preserve return value of efi_entry() in r4
 		mov	r4, r0
-
-		@ our cache maintenance code relies on CP15 barrier instructions
-		@ but since we arrived here with the MMU and caches configured
-		@ by UEFI, we must check that the CP15BEN bit is set in SCTLR.
-		@ Note that this bit is RAO/WI on v6 and earlier, so the ISB in
-		@ the enable path will be executed on v7+ only.
-		mrc	p15, 0, r1, c1, c0, 0	@ read SCTLR
-		tst	r1, #(1 << 5)		@ CP15BEN bit set?
-		bne	0f
-		orr	r1, r1, #(1 << 5)	@ CP15 barrier instructions
-		mcr	p15, 0, r1, c1, c0, 0	@ write SCTLR
- ARM(		.inst	0xf57ff06f		@ v7+ isb	)
- THUMB(		isb						)
-
-0:		bl	cache_clean_flush
+		bl	cache_clean_flush
 		bl	cache_off
 
 		@ Set parameters for booting zImage according to boot protocol