mmc: dw_mmc-k3: Remove mshc alias support

mmc: dw_mmc-k3: Remove mshc alias support

Remove the long-deprecated mshc alias support, as the mmc core already
provides alias functionality through the standard mmc alias. This eliminates
the redundant dual-alias system. The driver now obtains the controller ID
from struct mmc_host::index(supplied by mmc alias) instead of the legacy mshc
alias.

dw_mci_hi6220_parse_dt() which parse mshc alias is used for hi6220, hi3660 and
hi3670. Given hi6220 never assigned mshc alias on the DTS files, and hi3360
and hi3670 share the same code, so with it removed, add a return value to
dw_mci_hs_set_timing() and let dw_mci_hi3660_init() check if index exceeds
TIMING_MODE in the firs place to bail out early, the same as before.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>