libc/i386/SYS.h: Remove unused LCALL macro

It appears that the only user of this macro was removed
with support for building a.out binaries in 2002 by commit
66422f5b7a.

Reviewed by:	imp, kib
Sponsored by:	DARPA
Differential Revision:	https://reviews.freebsd.org/D42997

lib/libc/i386/SYS.h

@@ -48,7 +48,4 @@
 			jb HIDENAME(cerror); ret;			\
 			END(__sys_##name)
 
-/* gas messes up offset -- although we don't currently need it, do for BCS */
-#define	LCALL(x,y)	.byte 0x9a ; .long y; .word x
-
 #define KERNCALL	int $0x80