PCI: Change pdev->rom_attr_enabled to single bit

PCI: Change pdev->rom_attr_enabled to single bit

Make 'rom_attr_enabled' a single bit in a bitfield and move it close to an
existing bitfield so that they can be merged.

This field is only used in 'drivers/pci/pci-sysfs.c' to store 0 or 1.

On x86_64, this shrinks the size of 'struct pci_dev' by 8 bytes from 3560
to 3552.

Link: https://lore.kernel.org/r/d7a34ad369336db73145c3efbade895e792a0ad3.1687105455.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>