Revert "arm64: reset: disable cache and MMU for safety"

This reverts commit 573a712.

The original patch disable cache and MMU, but in some cases, for example
the code is loaded into memory by hardware debugger, we need to flush
D-Cache before disable it in order to make sure the data is coherent
in the system, otherwise it will report "Synchronous Abort" when D-Cache
is disabled.

This patch revert the old one and the following patch will flush
the cache before disable it.

Signed-off-by: Jiafei Pan <[email protected]>

Author: JiafeiPan

arch/arm64/core/reset.S

@@ -58,10 +58,9 @@ SECTION_SUBSEC_FUNC(TEXT,_reset_section,__reset_prep_c)
 	b	out
 #endif /* CONFIG_ARMV8_R */
 2:
-	/* Disable alignment fault checking, disable D-Cache, I-Cache, MMU for safety */
+	/* Disable alignment fault checking */
 	mrs	x0, sctlr_el2
-	mov	x1, #(SCTLR_A_BIT | SCTLR_C_BIT | SCTLR_M_BIT | SCTLR_I_BIT)
-	bic	x0, x0, x1
+	bic	x0, x0, SCTLR_A_BIT
 	msr	sctlr_el2, x0
 	isb