openvswitch: Shrink sw_flow_mask by 8 bytes (64-bit) or 4 bytes (32-bit).

We won't normally have a ton of flow masks but using a size_t to store
values no bigger than sizeof(struct sw_flow_key) seems excessive.

This reduces sw_flow_key_range and sw_flow_mask by 4 bytes on 32-bit
systems.  On 64-bit systems it shrinks sw_flow_key_range by 12 bytes but
sw_flow_mask only by 8 bytes due to padding.

Compile tested only.
Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Andy Zhou <azhou@nicira.com>
Signed-off-by: Jesse Gross <jesse@nicira.com>

net/openvswitch/flow.h

@@ -122,8 +122,8 @@ struct sw_flow_key {
 } __aligned(BITS_PER_LONG/8); /* Ensure that we can do comparisons as longs. */
 
 struct sw_flow_key_range {
-	size_t start;
-	size_t end;
+	unsigned short int start;
+	unsigned short int end;
 };
 
 struct sw_flow_mask {