HID: amd_sfh: Handle condition of "no sensors" for SFH1.1

Based on num_hid_devices, each sensor device registers to HID. If
"no sensors" then amd_sfh work initialization and scheduling
doesn’t make sense and return ENODEV to stop driver probe.
Hence add a check for num_hid_devices to handle special
case in the situation of "no sensors" for SFH1.1.

Fixes: 93ce5e02 ("HID: amd_sfh: Implement SFH1.1 functionality")
Signed-off-by: Basavaraj Natikar <Basavaraj.Natikar@amd.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>