fix(resume): check for presence of /sys/power/resume

On platforms where the kernel is built without suspend/resume support we
see "cat: /sys/power/resume: No such file or directory" message when
creating an initrd image. Check for the presence of /sys/power/resume
first before reading it.

Signed-off-by: Dan Horák <dan@danny.cz>

modules.d/95resume/module-setup.sh

@@ -13,7 +13,7 @@ check() {
     # Only support resume if hibernation is currently on
     # and no swap is mounted on a net device
     [[ $hostonly ]] || [[ $mount_needs ]] && {
-        swap_on_netdevice || [[ "$(cat /sys/power/resume)" == "0:0" ]] && return 255
+        swap_on_netdevice || [[ -f /sys/power/resume && "$(cat /sys/power/resume)" == "0:0" ]] && return 255
     }
 
     return 0