mtd: rawnand: gpmi: add 'support_edo_timing' in gpmi_devdata

Introduce a boolean flag, 'support_edo_timing', within gpmi_devdata to
simplify the logic check in gpmi_setup_interface(). This is made in
preparation for adding support for imx8qxp gpmi.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20240520-gpmi_nand-v2-3-e3017e4c9da5@nxp.com