spi: fspi: dynamically alloc AHB memory

Apply patch from NXP upstream repo to
dynamically allocate AHB memory as needed.

Signed-off-by: Adam Ford <aford173@gmail.com>
Signed-off-by: Han Xu <han.xu@nxp.com>

Link: https://lore.kernel.org/r/20200126140913.2139260-2-aford173@gmail.com


Signed-off-by: Mark Brown <broonie@kernel.org>