meta-gpe: use BPN in SRC_URI

Fixed SRC_URI:
* ${PN} -> ${BPN}, use ${BP} if it was ${PN}-${PV}
* ${P} -> ${BP}

Otherwise we would meet do_fetch errors when we do the multilib, native
or nativesdk build.

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>