ARM: 8189/1: arm64:add bitrev.h file to support rbit instruction

This patch add bitrev.h file to support rbit instruction,
so that we can do bitrev operation by hardware.

Signed-off-by: Yalin Wang <[e-mail]>
Acked-by: Will Deacon <[e-mail]>
Signed-off-by: Russell King <[e-mail]>

arch/arm64/Kconfig

···
 	select HARDIRQS_SW_RESEND
 	select HAVE_ALIGNED_STRUCT_PAGE if SLUB
 	select HAVE_ARCH_AUDITSYSCALL
+	select HAVE_ARCH_BITREVERSE
 	select HAVE_ARCH_JUMP_LABEL
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_SECCOMP_FILTER

arch/arm64/include/asm/bitrev.h

···
+#ifndef __ASM_BITREV_H
+#define __ASM_BITREV_H
+static __always_inline __attribute_const__ u32 __arch_bitrev32(u32 x)
+{
+	__asm__ ("rbit %w0, %w1" : "=r" (x) : "r" (x));
+	return x;
+}
+
+static __always_inline __attribute_const__ u16 __arch_bitrev16(u16 x)
+{
+	return __arch_bitrev32((u32)x) >> 16;
+}
+
+static __always_inline __attribute_const__ u8 __arch_bitrev8(u8 x)
+{
+	return __arch_bitrev32((u32)x) >> 24;
+}
+
+#endif