arm-bsp: Move to linux-linaro-arm for fvp-base and foundation-armv8

Change fvp-base and foundation-armv8 kernel from linux-yocto_5.4
to linux-linaro-arm_4.19 because some drivers are not available.
Furthermore, for fvp-base the linaro kernel comes with the dts
file removing the needs to support it on our side.

Change-Id: I844d92f173406542c2bad8d89793513f8bc28fd1
Signed-off-by: luca fancellu <luca.fancellu@arm.com>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>