MIPS: SEAD3: Remove custom read_persistent_clock

The SEAD3 board defines a custom implementation of read_persistent_clock
which does exactly the same dummy operation as the generic weak version.
Remove the not really implemented custom version.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/14064/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/mti-sead3/sead3-time.c

@@ -63,12 +63,6 @@ static unsigned int __init estimate_cpu_frequency(void)
 	return freq ;
 }
 
-void read_persistent_clock(struct timespec *ts)
-{
-	ts->tv_sec = 0;
-	ts->tv_nsec = 0;
-}
-
 int get_c0_perfcount_int(void)
 {
 	if (gic_present)