PCI/VGA: Correct vga_str_to_iostate() io_state parameter type

Previously vga_str_to_iostate() took "int *io_state", but vga_arb_write()
is the only caller and it passes "unsigned int *".  Make the
vga_str_to_iostate() parameter type "unsigned int *" to match.

[bhelgaas: commit log]
Link: https://lore.kernel.org/r/20230808223412.1743176-2-sui.jingfeng@linux.dev


Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>