[MIPS] <asm/mipsregs.h>: Update coprocessor register access macros

Signed-off-by: Shinya Kuribayashi <skuribay@ruby.dti.ne.jp>
diff --git a/board/gth2/gth2.c b/board/gth2/gth2.c
index 6da80dc..9bc4d3f 100644
--- a/board/gth2/gth2.c
+++ b/board/gth2/gth2.c
@@ -135,7 +135,7 @@
 
 	*sys_counter = 0x100; /* Enable 32 kHz oscillator for RTC/TOY */
 
-	proc_id = read_32bit_cp0_register(CP0_PRID);
+	proc_id = read_c0_prid();
 
 	switch (proc_id >> 24) {
 	case 0: