mmc: omap_hsmmc: Cleanup bitmap definitions of Interrupt Register

Define the most frequently used bitmasks of the Interrupt Enable /
Interrupt Status register with consistent naming ( with _EN suffix).

Use meaningful concatenation of bitfields for INT_EN_MASK, which shows
which interrupts are enabled by default.  No functional changes.

Signed-off-by: Venkatraman S <svenkatr@ti.com>
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Chris Ball <cjb@laptop.org>