mtd: spi-nor: Allow Cadence QSPI support for ARM64

Allow ARM64 support for the Cadence QSPI interface by
adding ARM64 as a dependency.

Signed-off-by: Thor Thayer <thor.thayer@linux.intel.com>
Reviewed-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: Cyrille Pitchen <cyrille.pitchen@wedev4u.fr>