wimax/i2400m: rename misleading I2400M_PL_PAD to I2400M_PL_ALIGN

The constant is being use as an alignment factor, not as a padding
factor; made reading/reviewing the code quite confusing.

Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>
diff --git a/include/linux/wimax/i2400m.h b/include/linux/wimax/i2400m.h
index d5148a7..433693e 100644
--- a/include/linux/wimax/i2400m.h
+++ b/include/linux/wimax/i2400m.h
@@ -266,7 +266,7 @@
 
 /* Misc constants */
 enum {
-	I2400M_PL_PAD = 16,	/* Payload data size alignment */
+	I2400M_PL_ALIGN = 16,	/* Payload data size alignment */
 	I2400M_PL_SIZE_MAX = 0x3EFF,
 	I2400M_MAX_PLS_IN_MSG = 60,
 	/* protocol barkers: sync sequences; for notifications they