rtc: tps65910: Remove redundant dev_warn() and do not check for 0 return after calling platform_get_irq()

It is not possible for platform_get_irq() to return 0. Use the
return value from platform_get_irq().

And there is no need to call the dev_warn() function directly to print
a custom message when handling an error from platform_get_irq()
function as it is going to display an appropriate error message
in case of a failure.
Signed-off-by: Ruan Jinjie <ruanjinjie@huawei.com>
Link: https://lore.kernel.org/r/20230803080713.4061782-3-ruanjinjie@huawei.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>