cmd/internal/obj/x86: VPSHUFD takes an unsigned byte.

VPSHUFD should take an unsigned argument to be consistent with
PSHUFD. Also fix all usage.

Fixes #16499

Change-Id: Ie699c102afed0379445914a251710365b14d89b6
Reviewed-on: https://go-review.googlesource.com/25383
Run-TryBot: Ilya Tocar <ilya.tocar@intel.com>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/internal/obj/x86/asm6.go

@@ -855,8 +855,8 @@ var yvex_ri3 = []ytab{
 }
 
 var yvex_xyi3 = []ytab{
-	{Yi8, Yxm, Yxr, Zvex_i_rm_r, 2},
-	{Yi8, Yym, Yyr, Zvex_i_rm_r, 2},
+	{Yu8, Yxm, Yxr, Zvex_i_rm_r, 2},
+	{Yu8, Yym, Yyr, Zvex_i_rm_r, 2},
 }
 
 var yvex_yyi4 = []ytab{ //TODO don't hide 4 op, some version have xmm version

src/crypto/sha256/sha256block_amd64.s

@@ -302,7 +302,7 @@
 	ADDL    y0, y2;                      \ // y2 = S1 + CH					// --
 	;                                    \
 	VPXOR   XTMP4, XTMP3, XTMP1;         \ // XTMP1 = s0
-	VPSHUFD $-6, XDWORD3, XTMP2;         \ // XTMP2 = W[-2] {BBAA}
+	VPSHUFD $0xFA, XDWORD3, XTMP2;       \ // XTMP2 = W[-2] {BBAA}
 	ORL     T1, y3;                      \ // y3 = MAJ = (a|c)&b)|(a&c)             // MAJ
 	ADDL    y1, h;                       \ // h = k + w + h + S0                    // --
 	;                                    \