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/fpga/openpiton/platform.c

@@ -185,9 +185,6 @@ const struct sbi_platform_operations platform_ops = {
 	.ipi_send = clint_ipi_send,
 	.ipi_clear = clint_ipi_clear,
 	.timer_init = openpiton_timer_init,
-	.timer_value = clint_timer_value,
-	.timer_event_start = clint_timer_event_start,
-	.timer_event_stop = clint_timer_event_stop,
 };
 
 const struct sbi_platform platform = {