Fix bitbake license warnings

The following warnings are seen when building fvp-base
WARNING: fvp-base-native-r11p7-30rel0-r0 do_populate_lic: fvp-base-native: No generic license file exists for: GPL in any provider
WARNING: fvp-base-native-r11p7-30rel0-r0 do_populate_lic: fvp-base-native: No generic license file exists for: Apache in any provider
Correct the license names to the expected strings resolves the issue

Change-Id: Ia4962736840de8b4a02d0c9d59b7c14c9999997c
Signed-off-by: Jon Mason <jon.mason@arm.com>