[MIPS] kgdb: Let gcc compute the array size itself.

This is the same method as used in the serial driver.
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/mips-boards/generic/gdb_hook.c

@@ -25,7 +25,7 @@
 #include <asm/serial.h>
 #include <asm/io.h>
 
-static struct serial_state rs_table[RS_TABLE_SIZE] = {
+static struct serial_state rs_table[] = {
 	SERIAL_PORT_DFNS	/* Defined in serial.h */
 };