Constify received GDB packet

v2:
- Split work into separate patches

The received packet will not be altered in any of the processing functions.
Some it can be made "const".

Change-Id: I7bb410224cf6daa74a6c494624176ccb9ae638ac
Signed-off-by: Christian Eggers <ceggers@gmx.de>
Reviewed-on: http://openocd.zylin.com/1919
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>

src/target/smp.c

@@ -56,7 +56,7 @@
 
 /* packet j :smp status request */
 int gdb_read_smp_packet(struct connection *connection,
-		char *packet, int packet_size)
+		char const *packet, int packet_size)
 {
 	struct target *target = get_target_from_connection(connection);
 	int retval = ERROR_OK;
@@ -77,7 +77,7 @@ int gdb_read_smp_packet(struct connection *connection,
 
 /* J :  smp set request */
 int gdb_write_smp_packet(struct connection *connection,
-		char *packet, int packet_size)
+		char const *packet, int packet_size)
 {
 	struct target *target = get_target_from_connection(connection);
 	char *separator;