[gdb/tdep] Remove includes of gdbsupport/common-defs.h

In commit 18d2988 ("gdb, gdbserver, gdbsupport: remove includes of early
headers") all includes of gdbsupport/common-defs.h where removed, but
commit c1cdee0 ("gdb: LoongArch: Add support for hardware watchpoint")
reintroduced some.

Fix this by removing them.

Tested by doing this on x86_64-linux:
...
$ make \
    nat/loongarch-hw-point.o \
    nat/loongarch-linux.o \
    nat/loongarch-linux-hw-point.o
  CXX    nat/loongarch-hw-point.o
  CXX    nat/loongarch-linux.o
  CXX    nat/loongarch-linux-hw-point.o
...

Approved-By: Simon Marchi <simon.marchi@efficios.com>

gdb/nat/loongarch-hw-point.c

@@ -18,7 +18,6 @@
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
-#include "gdbsupport/common-defs.h"
 #include "gdbsupport/break-common.h"
 #include "gdbsupport/common-regcache.h"
 #include "loongarch-hw-point.h"

gdb/nat/loongarch-linux-hw-point.c

@@ -18,7 +18,6 @@
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>. */
 
-#include "gdbsupport/common-defs.h"
 #include "gdbsupport/break-common.h"
 #include "gdbsupport/common-regcache.h"
 #include "nat/linux-nat.h"

gdb/nat/loongarch-linux.c

@@ -18,7 +18,6 @@
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
-#include "gdbsupport/common-defs.h"
 #include "gdbsupport/break-common.h"
 #include "nat/linux-nat.h"
 #include "nat/loongarch-linux-hw-point.h"