drivers: flash: Support XIP for MAX32 SPIXF flash

Properly configure the MAX32 SPIXF peripheral to use the SPIXF controller
for transparent memory mapped reads, and enable the SPIXF main controller
and use it for writes.

Add support for testing XIP support to the nocopy sample, which requires
flashing with OpenOCD with MAX32690 QSPI flash support.

Signed-off-by: Pete Johanson <pete.johanson@analog.com>