MAINTAINERS: Mark hyperv_fb driver Obsolete

MAINTAINERS: Mark hyperv_fb driver Obsolete

The hyperv_fb driver is deprecated in favor of Hyper-V DRM driver. Split
the hyperv_fb entry from the hyperv drivers list, mark it obsolete.

Signed-off-by: Prasanna Kumar T S M <ptsm@linux.microsoft.com>
Reviewed-by: Saurabh Sengar <ssengar@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Wei Liu <wei.liu@kernel.org>