empdcd: fix compile on platforms with VFP

empdcd: fix compile on platforms with VFP

on platforms with VFP/hardfloat ld fails with:
empcd uses VFP register arguments, empcd.o does not
empcd uses VFP register arguments, keyeventtable.o does not
empcd uses VFP register arguments, support/mpc-0.12.2/src/libmpdclient.o does not

append to CFLAGS instead of overwrite

Signed-off-by: Dirk Neukirchen <dirkneukirchen@web.de>
Signed-off-by: Florian Fainelli <florian@openwrt.org>
git-svn-id: svn://svn.openwrt.org/openwrt/packages@40787 3c298f89-4303-0410-b956-a3cf2f4a3e73