mmc: irq: Remove IRQF_DISABLED

Since commit [e58aa3d2: genirq: Run irq handlers with interrupts
disabled], we run all interrupt handlers with interrupts disabled
and we even check and yell when an interrupt handler returns with
interrupts enabled (see commit [b738a50a: genirq: Warn when handler
enables interrupts]).

So now this flag is a NOOP and can be removed.

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Acked-by: Kishore Kadiyala <kishore.kadiyala@ti.com>
Acked-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Chris Ball <cjb@laptop.org>