staging: lustre: ldlm_extent.c: replace IS_PO2 by is_power_of_2

Replaces IS_PO2 by is_power_of_2. It is more accurate to use
is_power_of_2 since it returns 1 for numbers that are powers
of 2 only whereas IS_PO2 returns 1 for 0 and numbers that are
powers of 2.
Signed-off-by: Aya Mahfouz <mahfouz.saif.elyazal@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/ldlm/ldlm_extent.c

@@ -149,7 +149,7 @@ static inline int lock_mode_to_index(ldlm_mode_t mode)
 	int index;
 
 	LASSERT(mode != 0);
-	LASSERT(IS_PO2(mode));
+	LASSERT(is_power_of_2(mode));
 	for (index = -1; mode; index++)
 		mode >>= 1;
 	LASSERT(index < LCK_MODE_NUM);