MLK-14748 clocksource: imx-tpm: Increase the min_delta

MLK-14748 clocksource: imx-tpm: Increase the min_delta

The current min_delta for TPM clock event is 2 ticks which
is too small. As the TPM is running at 3MHz, 2 ticks equal
2/3 us. According to our testing, the interrupt latency will
be longer than this min_delta, especially when GPU is running.

This patch changed the min_delta to 300 which give the system
around 100us for interrupt handling in case the "set_next_event"
call is interrupted by other signals.

Also a simple validation code is added before the function returns.

Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com>
Signed-off-by: Bai Ping <ping.bai@nxp.com>
(cherry picked from commit 4f882165cc31672f3c98de74ab02b757cb96ad26)