libchkstk.S: Remove stray sub from x86 ___chkstk_ms

Thanks to Felipe Garcia for catching this. That sub was a leftover from
an earlier version which did not push eax/rax. I missed it when updating
to the current version.

Author: skeeto

src/libchkstk.S

@@ -57,7 +57,6 @@ ___chkstk_ms:
 	test %eax, (%ecx)	// commit page (two instruction bytes)
 1:	cmp  %eax, %ecx
 	ja   0b
-	sub  %esp, %eax
 	pop  %ecx
 	pop  %eax
 	ret