[librm] Discard argument as part of return from real_call()

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/x86/include/librm.h

 #define REAL_CODE( asm_code_str )			\
 	"push $1f\n\t"					\
 	"call real_call\n\t"				\
-	"addl $4, %%esp\n\t"				\
 	TEXT16_CODE ( "\n1:\n\t"			\
 		      asm_code_str			\
 		      "\n\t"				\

src/arch/x86/transitions/librm.S

 rc_pmode:
 	/* Restore registers and return */
 	popal
-	ret
+	ret	$4
 
 
 	/* Function vector, used because "call xx(%sp)" is not a valid