board: novtech: meerkat96: use correct mmc driver

When the board was originally submitted, it was attempting to use the
ESDHC driver. The board uses the USDHC driver.

Signed-off-by: Carl Gelfand <carl@novtech.com>
Cc: Shawn Guo <shawn.guo@kernel.org> (maintainer:MEERKAT96 BOARD)
Acked-by: Shawn Guo <shawnguo@kernel.org>