video/vga: Add VGA_IS0_R

video/vga: Add VGA_IS0_R

Add a proper name for the "Input status register 0" IO address.
Currently we have some code that does reads using the aliasing
VGA_MSR_W define, making it unclear what register we're
actually reading.

v2: Remove stray '?'

Cc: Helge Deller <deller@gmx.de>
Cc: linux-fbdev@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patch.msgid.link/20251209075549.14051-1-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Helge Deller <deller@gmx.de>