rtc: optee: Fix error code in optee_rtc_read_alarm()

Return "optee_alarm" instead of "alarm".  The "alarm" pointer is a valid
pointer and not an error pointer.

Fixes: 6266aea8 ("rtc: optee: add alarm related rtc ops to optee rtc driver")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/9e3718fe1128964907619ad325c0c5f5c1354ace.1758182509.git.dan.carpenter@linaro.org


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>