udev-cache: choose a more descriptive cache filename

udev-cache: choose a more descriptive cache filename

"/etc/dev.tar.gz" doesn't adequately imply that udev-cache maintains it.
Instead, call it "/etc/udev-cache.tar.gz".

(From OE-Core rev: b33c678e2a5d42138a15b69802c5ddd109cb3b55)

Signed-off-by: Richard Tollerton <rich.tollerton@ni.com>
Signed-off-by: Ben Shelton <ben.shelton@ni.com>
Acked-by: Gratian Crisan <gratian.crisan@ni.com>
Acked-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>