boards: arm: Add mcuboot flash partitions to mimxrt1064_evk

Adds flash partitions and chosen nodes to the mimxrt1064_evk device tree
to support mcuboot on the internal QSPI flash. This flash is rated for
100K minimum program-erase cycles per sector, therefore this partition
configuration supports approximately 100K / (1984/64) = 3225 upgrades.

Also enables FlexSPI flash driver XIP mode support on this board to
support mcuboot.

Signed-off-by: Maureen Helm <maureen.helm@nxp.com>