With the changes in the random tree, IRQF_SAMPLE_RANDOM is now a
no-op; interrupt randomness is now collected unconditionally in a very
low-overhead fashion; see commit 775f4b29

.  The IRQF_SAMPLE_RANDOM
flag was scheduled to be removed in 2009 on the
feature-removal-schedule.

The flag was only commented-out in the driver, but we should just
remove it altogether.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Felipe Balbi <balbi@ti.com>