net: stmmac: sti: Switch from CONFIG_PM_SLEEP guards to pm_sleep_ptr()

net: stmmac: sti: Switch from CONFIG_PM_SLEEP guards to pm_sleep_ptr()

Letting the compiler remove these functions when the kernel is built
without CONFIG_PM_SLEEP support is simpler and less error prone than the
use of #ifdef based kernel configuration guards.

Signed-off-by: Raphael Gallais-Pou <rgallaispou@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Yanteng Si <si.yanteng@linux.dev>
Link: https://patch.msgid.link/20250109155842.60798-1-rgallaispou@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>