mmc: xenon_sdhci: Add missing common host capabilities

Use mmc_of_parse() to set the common host properties. That includes
"bus-width", so parsing it can be removed from the driver.

But more importantly, "non-removable" is now respected, which fixes
the usage of eMMC.

Signed-off-by: Andre Heider <a.heider@gmail.com>
Reviewed-by: Konstantin Porotchkin <kostap@marvell.com>
Tested-by: Marek Behún <marek.behun@nic.cz>