The SD UHS SDR12, SDR25, SDR50, SDR104, DDR50 and MMC HS200, HS400
modes all use 1.8V signaling, while all the legacy modes use 3.3V
signaling. While there are extra modes which use 1.2V signaling,
the existing hardware does not support those.

Simplify the pinmux such that 3.3V signaling implies legacy mode
pinmux and the rest implies UHS mode pinmux. This prevents the
massive case statement from growing further. Moreover, it fixes
an edge case where during SD 1.8V switch, the bus mode is still
set to default while the signaling is already set to 1.8V, which
results in an attempt to communicate with a 1.8V card using pins
in 3.3V mode and thus communication failure.
Signed-off-by: NMarek Vasut <marek.vasut+renesas@gmail.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>