efl: fix build by adding -fPIC to CFLAGS

on armv7/cortexa8 efl fails with:

| ld: error: modules/evas/image_loaders/png/bin_evas_evas_cserve2_slave-evas_image_load_png.o: requires unsupported dynamic reloc R_ARM_MOVW_ABS_NC; recompile with -fPIC
| ld: error: modules/evas/image_loaders/png/bin_evas_evas_cserve2_slave-evas_image_load_png.o: requires unsupported dynamic reloc R_ARM_MOVW_ABS_NC; recompile with -fPIC

Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>