vgaarb: avoid -Wempty-body warnings

Building with W=1 shows a few warnings for an empty macro:

drivers/gpu/drm/qxl/qxl_drv.c: In function 'qxl_pci_probe':
drivers/gpu/drm/qxl/qxl_drv.c:131:50: error: suggest braces around empty body in an 'if' statement [-Werror=empty-body]
  131 |                 vga_put(pdev, VGA_RSRC_LEGACY_IO);
      |                                                  ^
drivers/gpu/drm/qxl/qxl_drv.c: In function 'qxl_pci_remove':
drivers/gpu/drm/qxl/qxl_drv.c:159:50: error: suggest braces around empty body in an 'if' statement [-Werror=empty-body]
  159 |                 vga_put(pdev, VGA_RSRC_LEGACY_IO);

Change this to an inline function to make it more robust and avoid
the warning.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210322105307.1291840-2-arnd@kernel.org