drivers: mcux_gpt_timer: Enabled GPT timer on MIMXRT1064 EVK

This enables the GPT timer for use as a hardware clock on the
MIMXRT1064. The timer will be disabled when builds use the GPT timer as
a counter, and the build will fall back to using the Cortex M systick as
a timer. This was tested using the kernel tickless test, to verify the
driver functions as expected.

Signed-off-by: Daniel DeGrasse <daniel.degrasse@nxp.com>