V4L/DVB (4876): budget-ci IR: support EVIOCGPHYS

This patch adds a 'phys' string, of the same form as used by various other
DVB cards' IR drivers, for access by any program which uses the EVIOCPHYS
ioctl or may read /sys/class/input/*/phys (e.g. udev) to identify input
device nodes.
Taken from Darren Salt's dvb-ir patchset.

Signed-off-by: Darren Salt <linux@youmustbejoking.demon.co.uk>
Signed-off-by: David Hardeman <david@hardeman.nu>
Signed-off-by: Andrew de Quincey <adq_dvb@lidskialf.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>