mmc: remove the MMC_MODE_HC flag

High capacity support is not a host capability, but a device capability
that is queried via the OCR. The flag in the operating conditions
request argument can just be set unconditionally. This matches the Linux
implementation.

[panto] Hand merged and renumbering MMC_MODE_DDR_52MHz.

Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
Cc: Pantelis Antoniou <pantelis.antoniou@konsulko.com>