spi: nxp-fspi: Add support for IP read only

Add support for disabling AHB bus and read entire flash contents via IP
bus only. Please note, this enables IP bus read using a quirk which can
be enabled directly in device-type data or in existence of an errata
where AHB bus may need to be disabled.

Signed-off-by: Kuldeep Singh <kuldeep.singh@nxp.com>
Acked-by: Jagan Teki <jagan@amarulasolutions.com>