ARM: multi_v7_defconfig: add NXP graphics drivers

Enable drivers to support NXP graphics IPs such as:
- Etnaviv (e.g. i.MX6)
- DCU (e.g. Vybrid LS1021A)
- mxsfb (e.g. i.MX6UL/ULL/7)

Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>