mmc: omap: fix mmc_omap_report_irq to use dev_dbg macros

The function mmc_omap_report_irq uses raw printks and the actual output
was disabled by a static variable. Make the function use dev_vdbg macro
and use it under the standard CONFIG_MMC_DEBUG flag.

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