drm/nouveau: remove set but not used variable ‘pdev’ in nouveau_bios_init

Fix follow warning:
drivers/gpu/drm/nouveau/nouveau_bios.c:2086:18: warning: variable ‘pdev’ set but not used [-Wunused-but-set-variable]
  struct pci_dev *pdev;
                  ^~~~

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Ye Bin <yebin10@huawei.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20210123013014.3815870-1-yebin10@huawei.com