drm/mgag200: Don't read-back PCI option register before writing

Remove the read operation from mgag200_init_pci_options(). It was
incorrectly added while refactoring the code. Reading the PCI option
register clears the register's new value and subsequently leads to
re-writing the old value.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Fixes: ce19021 ("drm/mgag200: Move PCI-option setup into model-specific code")
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Jocelyn Falempe <jfalempe@redhat.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Link: https://patchwork.freedesktop.org/patch/msgid/20220708072114.13960-1-tzimmermann@suse.de

drivers/gpu/drm/mgag200/mgag200_drv.c

@@ -28,12 +28,6 @@ int mgag200_init_pci_options(struct pci_dev *pdev, u32 option, u32 option2)
 	struct device *dev = &pdev->dev;
 	int err;
 
-	err = pci_read_config_dword(pdev, PCI_MGA_OPTION, &option);
-	if (err != PCIBIOS_SUCCESSFUL) {
-		dev_err(dev, "pci_read_config_dword(PCI_MGA_OPTION) failed: %d\n", err);
-		return pcibios_err_to_errno(err);
-	}
-
 	err = pci_write_config_dword(pdev, PCI_MGA_OPTION, option);
 	if (err != PCIBIOS_SUCCESSFUL) {
 		dev_err(dev, "pci_write_config_dword(PCI_MGA_OPTION) failed: %d\n", err);