mmc: xenon_sdhci: Remove duplicated macros

There is no need to define the same macros in drivers.
All macros have been added by commit 17a42abb ("mmc: Define timing
macro's").

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>