cmd/internal/obj/x86: rename POPCNT to POPCNTQ

Ilya added POPCNT in a CL earlier this month but it's really only POPCNTQ.
The other forms still need to be added.

For #4816.

Change-Id: I1186850d32ad6d5777475c7808e6fc9d9133e118
Reviewed-on: https://go-review.googlesource.com/18848Reviewed-by: Rob Pike <r@golang.org>

src/cmd/internal/obj/x86/a.out.go

@@ -181,7 +181,9 @@ const (
 	APAUSE
 	APOPAL
 	APOPAW
-	APOPCNT
+	APOPCNTW
+	APOPCNTL
+	APOPCNTQ
 	APOPFL
 	APOPFW
 	APOPL

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

@@ -149,7 +149,9 @@ var Anames = []string{
 	"PAUSE",
 	"POPAL",
 	"POPAW",
-	"POPCNT",
+	"POPCNTW",
+	"POPCNTL",
+	"POPCNTQ",
 	"POPFL",
 	"POPFW",
 	"POPL",

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

@@ -1208,7 +1208,7 @@ var optab =
 	{APMULULQ, ymm, Py1, [23]uint8{0xf4, Pe, 0xf4}},
 	{APOPAL, ynone, P32, [23]uint8{0x61}},
 	{APOPAW, ynone, Pe, [23]uint8{0x61}},
-	{APOPCNT, yml_rl, Pfw, [23]uint8{0xb8}},
+	{APOPCNTQ, yml_rl, Pfw, [23]uint8{0xb8}},
 	{APOPFL, ynone, P32, [23]uint8{0x9d}},
 	{APOPFQ, ynone, Py, [23]uint8{0x9d}},
 	{APOPFW, ynone, Pe, [23]uint8{0x9d}},