Simplify detection of Raspberry Pi devices

[missionfloyd]

Replaces this roundabout method...

e-Paper/RaspberryPi_JetsonNano/python/lib/waveshare_epd/epdconfig.py

Lines 304 to 310 in ecdd8cf

	if sys.version_info[0] == 2:
	process = subprocess.Popen("cat /proc/cpuinfo | grep Raspberry", shell=True, stdout=subprocess.PIPE)
	else:
	process = subprocess.Popen("cat /proc/cpuinfo | grep Raspberry", shell=True, stdout=subprocess.PIPE, text=True)
	output, _ = process.communicate()
	if sys.version_info[0] == 2:
	output = output.decode(sys.stdout.encoding)

...with a simple check for either /sys/bus/platform/drivers/gpiomem-bcm2835 or /sys/bus/platform/drivers/rpi-gpiomem, as in setup.py.

Similarly, in epdconfig for 13in3E, reads files directly, rather than capturing the output of cat.