mmc: core: fix bus-width selection in HS400 mode

During card initialization, for hs400 enhanced strobe
mode we already set the bus width to 8 as part of
mmc_select_hs400.
i.e: mmc_init_card->mmc_select_timing->mmc_select_hs400

Commit 5a86b115 ("mmc: core: fix multi-bit bus width
without high-speed mode") modified bus width selection mode
for hs400(mmc_select_bus_width is being called twice now)
which is resulting in switch command failure(-110 error).

Fix this by adding condition to check if hs400 is supported
before bus-width selection.

Change-Id: I698260599276a251ffbe2f242175be0dc51a91de
Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>