crypto: x86/chacha20 - satisfy stack validation 2.0

The new stack validator in objdump doesn't like directly assigning r11
to rsp, warning with something like:

warning: objtool: chacha20_4block_xor_ssse3()+0xa: unsupported stack pointer realignment
warning: objtool: chacha20_8block_xor_avx2()+0x6: unsupported stack pointer realignment

This fixes things up to use code similar to gcc's DRAP register, so that
objdump remains happy.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Fixes: baa41469a7b9 ("objtool: Implement stack validation 2.0")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

arch/x86/crypto/chacha20-avx2-x86_64.S

@@ -45,7 +45,7 @@ ENTRY(chacha20_8block_xor_avx2)
 
 	vzeroupper
 	# 4 * 32 byte stack, 32-byte aligned
-	mov		%rsp, %r8
+	lea		8(%rsp),%r10
 	and		$~31, %rsp
 	sub		$0x80, %rsp
 
@@ -443,6 +443,6 @@ ENTRY(chacha20_8block_xor_avx2)
 	vmovdqu		%ymm15,0x01e0(%rsi)
 
 	vzeroupper
-	mov		%r8,%rsp
+	lea		-8(%r10),%rsp
 	ret
 ENDPROC(chacha20_8block_xor_avx2)

arch/x86/crypto/chacha20-ssse3-x86_64.S

@@ -160,7 +160,7 @@ ENTRY(chacha20_4block_xor_ssse3)
 	# done with the slightly better performing SSSE3 byte shuffling,
 	# 7/12-bit word rotation uses traditional shift+OR.
 
-	mov		%rsp,%r11
+	lea		8(%rsp),%r10
 	sub		$0x80,%rsp
 	and		$~63,%rsp
 
@@ -625,6 +625,6 @@ ENTRY(chacha20_4block_xor_ssse3)
 	pxor		%xmm1,%xmm15
 	movdqu		%xmm15,0xf0(%rsi)
 
-	mov		%r11,%rsp
+	lea		-8(%r10),%rsp
 	ret
 ENDPROC(chacha20_4block_xor_ssse3)