gmp: disable ASM for m68k coldfire

Some m68k assembly is used inside gmp, so disable it for
coldfire.

Fixes following autobuild error:
http://autobuild.buildroot.net/results/30ac7b7fdaa51c0fe4fcafbbb558d60cb3d9fe51/

Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/gmp/gmp.mk

@@ -12,8 +12,8 @@ GMP_LICENSE = LGPLv3+
 GMP_LICENSE_FILES = COPYING.LESSERv3
 GMP_DEPENDENCIES = host-m4
 
-# GMP doesn't support assembly for r6 ISA yet
-ifeq ($(BR2_mips_32r6)$(BR2_mips_64r6),y)
+# GMP doesn't support assembly for coldfire or mips r6 ISA yet
+ifeq ($(BR2_m68k_cf)$(BR2_mips_32r6)$(BR2_mips_64r6),y)
 GMP_CONF_OPTS += --disable-assembly
 endif