lib: time: update module enable MACRO

We'd better use correct way to check if module has enabled.
for we have 3 timer MACRO:
- CONFIG_TIMER
- CONFIG_SPL_TIMER
- CONFIG_TPL_TIMER

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>