imx-common: fix iomux settings

imx-common: fix iomux settings

When setting iomux for a pin mux, there is no need to check mux_ctrl_ofs.
Also If still checking mux_ctrl_ofs, we have no chance to set iomux
for i.MX7D IOMUXC_LPSR_SW_MUX_CTL_PAD_GPIO1_IO00, because the mux_ctrl_ofs
for this register is 0.

Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Tested-by: Fabio Estevam <fabio.estevam@freescale.com>