mtd: onenand: Enable compile testing of OMAP and Samsung drivers

OMAP and Samsung OneNAND drivers can be compile tested.  The OMAP
drivers still depends on mach header so limit the compile testing to
ARMv7.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>