devtools: select patches to check with git range

devtools: select patches to check with git range

Rather than default to origin/master.., it can be handy to choose the
range you want to check.

Example on a branch rebased on next-net:

Before:
$ ./devtools/checkpatches.sh
...
...
67/69 valid patches

After:
$ ./devtools/checkpatches.sh -r next-net/master..

3/3 valid patches

Signed-off-by: David Marchand <david.marchand@redhat.com>
Acked-by: Thomas Monjalon <thomas@monjalon.net>