[PATCH] LOG2: Alter get_order() so that it can make use of ilog2() on a constant

Alter get_order() so that it can make use of ilog2() on a constant to produce
a constant value, retaining the ability for an arch to override it in the
non-const case.

Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>