config: add secure.gp config entry
The AM62Px does not have GP support (only HS-FS). Therefore, building the bootloaders generate this error:
Image 'tiboot3-am62px-hs-evm.bin' is missing external blobs but is still functional: ti-fs-enc.bin sysfw-inner-cert OFCHK .config cp: cannot stat 'tiboot3-am62px-gp-evm.bin': No such file or directory
Introduce a new config field, gp, which tells whether we should copy the GP bootloaders or not.
Signed-off-by: Mattijs Korpershoek mkorpershoek@baylibre.com