mmc: dw_mmc: Factor out dw_mci_init_slot_caps

mmc: dw_mmc: Factor out dw_mci_init_slot_caps

commit a4faa4929ed3be15e2d500d2405f992f6dedc8eb upstream.

Factor out dw_mci_init_slot_caps to consolidate parsing
all differents types of capabilities from host contrllers.
No functional change intended.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Fixes: 800d78bfccb3 ("mmc: dw_mmc: add support for implementation specific callbacks")
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
[bwh: Backported to 3.16:
 - We don't set MMC_CAP_ERASE or MMC_CAP2_SDIO_IRQ_NOTHREAD capabilities
 - Fold in required changes to the exit path from commits 51da2240906c
   "mmc: dw_mmc: use mmc_regulator_get_supply to handle regulators" and
   3cf890fc42b2 "mmc: dw_mmc: Pass back errors from mmc_of_parse()"
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>