drm/ast: Do not enable PCI resources multiple times

Remove ast_init_pci_config() as the ast driver already enables the PCI
resources by calling pcim_enable_device().

Suggested-by: Sui Jingfeng <suijingfeng@loongson.cn>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Tested-by: Sui Jingfeng <suijingfeng@loongson.cn>
Link: https://patchwork.freedesktop.org/patch/msgid/20230712130826.3318-1-tzimmermann@suse.de