s390/boot: Add cmdline option to relocate lowcore

Now that everything has been converted, add the option
'relocate_lowcore' to enable relocating the lowcore.
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/boot/ipl_parm.c

@@ -311,5 +311,7 @@ void parse_boot_command_line(void)
 				prot_virt_host = 1;
 		}
 #endif
+		if (!strcmp(param, "relocate_lowcore") && test_facility(193))
+			relocate_lowcore = 1;
 	}
 }