lib: sbi: Simplify timer platform operations

Instead of having timer_value(), timer_event_start(), and
timer_event_stop() callbacks in platform operations, it will
be much simpler for timer driver to directly register these
operations as device to the sbi_timer implementation.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

platform/andes/ae350/platform.c

@@ -172,9 +172,6 @@ const struct sbi_platform_operations platform_ops = {
 	.ipi_clear    = plicsw_ipi_clear,
 
 	.timer_init	   = ae350_timer_init,
-	.timer_value	   = plmt_timer_value,
-	.timer_event_start = plmt_timer_event_start,
-	.timer_event_stop  = plmt_timer_event_stop,
 
 	.vendor_ext_provider = ae350_vendor_ext_provider
 };