mmc: exynos_dw_mmc: Don't call pinmux functions on ARM64 chips

mmc: exynos_dw_mmc: Don't call pinmux functions on ARM64 chips

Pinmux configuration on ARM64 platforms must be performed during startup
in pinctrl driver using info from device tree. exynos_pinmux_config()
and pinmux_decode_periph_id() are only available on ARM32 platforms, so
don't call those functions on ARM64 platforms. Instead of the latter
function, use "non-removable" property from device tree to derive the
dev_index value.

This fixes next linking errors on ARM64 platforms:

    ld: drivers/mmc/exynos_dw_mmc.o:
      in function `exynos_dwmci_get_config':
      undefined reference to `pinmux_decode_periph_id'
    ld: drivers/mmc/exynos_dw_mmc.o:
      in function `do_dwmci_init':
      undefined reference to `exynos_pinmux_config'

Fixes: a082a2dde061 ("EXYNOS5: DWMMC: Added FDT support for DWMMC")
Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>