Correct comments for x86_64 _vpaes_encrypt_core_2x.

The prose and the register listing didn't match. (I suspect I wrote the
register listing before I decided which preheat registers to preserve.)

Change-Id: Ib461573ea50fdf5a806266c22805f6ba3470a6ec
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/37425
Reviewed-by: Adam Langley <agl@google.com>

crypto/fipsmodule/aes/asm/vpaes-x86_64.pl

diff --git a/crypto/fipsmodule/aes/asm/vpaes-x86_64.pl b/crypto/fipsmodule/aes/asm/vpaes-x86_64.pl
index 45463e8..8cc6a1a 100644
--- a/crypto/fipsmodule/aes/asm/vpaes-x86_64.pl
+++ b/crypto/fipsmodule/aes/asm/vpaes-x86_64.pl
@@ -182,11 +182,11 @@
 ##
 ##  Inputs:
 ##     %xmm0 and %xmm6 = input
-##     %xmm12-%xmm15 as in _vpaes_preheat
+##     %xmm9 and %xmm10 as in _vpaes_preheat
 ##    (%rdx) = scheduled keys
 ##
 ##  Output in %xmm0 and %xmm6
-##  Clobbers  %xmm1-%xmm5, %xmm7-%xmm11, %r9, %r10, %r11, %rax
+##  Clobbers  %xmm1-%xmm5, %xmm7, %xmm8, %xmm11-%xmm13, %r9, %r10, %r11, %rax
 ##  Preserves %xmm14 and %xmm15
 ##
 ##  This function stitches two parallel instances of _vpaes_encrypt_core. x86_64