Add Marvell ArmadaXP and Armada38X to GENERIC config

Include source files and drivers for Marvell ArmadaXP and Armada38X
in GENERIC kernel config.

Submitted by: Michal Mazur <mkm@semihalf.com>

	      Rafal Kozik <rk@semihalf.com>

Obtained from: Semihalf
Sponsored by: Stormshield
Differential Revision: https://reviews.freebsd.org/D14747