checkpatch: prefer usleep_range over udelay

When possible, sleeping is (usually) better than delaying; however, don't
bother callers of udelay < 10us, as those cases are generally not worth
the switch to usleep

[akpm@linux-foundation.org: fix mismatched parentheses]
Signed-off-by: Patrick Pannuto <ppannuto@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>