spi: fsl_qspi: Fix issues on arm64

The address value and size value get from dts "reg" property have
type of u64 on arm64. If we assign those values to "u32" variables,
driver can't work correctly. Converting the type of those variables
to fdt_xxx_t.

Signed-off-by: Yuan Yao <yao.yuan@nxp.com>
Signed-off-by: Prabhakar Kushwaha <prabhakar@freescale.com>
Reviewed-by: York Sun <york.sun@nxp.com>