windows: address error reported by vet

https://storage.googleapis.com/go-build-log/489a6b5c/misc-vet-vetall_c1e51035.log
cmd/vendor/golang.org/x/sys/windows/asm_windows_amd64.s:12: [amd64] loadlibrary: wrong argument size 8; expected $...-24

Change-Id: I02e7c53216e2c55d0d062e50f72984228c214e23
Reviewed-on: https://go-review.googlesource.com/114082
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

windows/asm_windows_amd64.s

@@ -9,5 +9,5 @@
 TEXT ·getprocaddress(SB), 7, $0-32
 	JMP	syscall·getprocaddress(SB)
 
-TEXT ·loadlibrary(SB), 7, $0-8
+TEXT ·loadlibrary(SB), 7, $0-24
 	JMP	syscall·loadlibrary(SB)