kbuild: rpm-pkg: remove kernel-drm PROVIDES

This code was added more than 20 years ago. [1]

I checked the kernel spec files in Fedora and OpenSUSE, but did not
see 'kernel-drm'. I do not know if there exists a distro that uses it
in RPM dependency.

Remove this, and let's see if somebody complains about it.

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/commit/?id=6d956df7d6b716b28c910c4f5b360c4d44d96c4d



Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>