[ARM] pxa: remove IRQF_SAMPLE_RANDOM which is now a no-op

[ARM] pxa: remove IRQF_SAMPLE_RANDOM which is now a no-op

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 775f4b297b.  The IRQF_SAMPLE_RANDOM
flag was scheduled to be removed in 2009 on the
feature-removal-schedule, so this patch is preparation for the final
removal of this flag.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com>
Cc: Eric Miao <eric.y.miao@gmail.com>
Cc: Russell King <linux@arm.linux.org.uk>