Drop check for if parent subsystem is PCI

This check is completely wrong for mobile GPUs where GPU are internal
and are not attached through PCI subsystem,

P: /devices/platform/display-engine/drm/card1
N: dri/card1
L: 0
S: dri/by-path/platform-display-engine-card
E: DEVPATH=/devices/platform/display-engine/drm/card1
E: DEVNAME=/dev/dri/card1
E: DEVTYPE=drm_minor
E: MAJOR=226
E: MINOR=1
E: SUBSYSTEM=drm
E: USEC_INITIALIZED=4239383
E: ID_PATH=platform-display-engine
E: ID_PATH_TAG=platform-display-engine
E: ID_FOR_SEAT=drm-platform-display-engine
E: DEVLINKS=/dev/dri/by-path/platform-display-engine-card
E: TAGS=:master-of-seat:seat:uaccess:

For example, on A64 platform, the KMS capable card is card1 which is not
attached with PCI.