imx: cpu: update cpu file to support i.MX8M

Update get_reset_cause to reflect i.MX8M
Compile out get_ahb_clk and set_chipselect_size for i.MX8M

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Stefano Babic <sbabic@denx.de>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Reviewed-by: Stefano Babic <sbabic@denx.de>
1 file changed