scripts/patch-kernel.sh: do not try to check files after patch

scripts/patch-kernel.sh: do not try to check files after patch

Since we are not using patch -b, *.orig files are only created when
there are conflicts, or never according to posix patch.

As such, it doesn't really make sense to always delete *.orig files
presuming they are patch backups, even if they are patch backups.
Doing so is both deleting potentially useful information for failed
patch applications and creating hard to diagnose bugs [1].

In a similar vein, checking for *.rej files does not add any value
since we're already checking the patch command's return code.

[1]: https://github.com/openwrt/packages/issues/27485

Signed-off-by: George Tsiamasiotis <george@tsiamasiotis.gr>
Link: https://github.com/openwrt/openwrt/pull/20141
Signed-off-by: Robert Marko <robimarko@gmail.com>