trim /cache partition on suspend...

...if the partition has not been trimmed for more than 15 minutes
and no media playback is happening.

Requires fstrim binary and suspend_trim helper script in /sbin
directory (cf. commit 'Fancy Kernel r29' in fancykernel-RAMDISK
branch).

Signed-off-by: Willi Ye <williye97@gmail.com>

Conflicts:
	init/main.c

Conflicts:
	init/main.c