gpio_brcmstb: Allow to build for ARCH_BCM2835

gpio-brcmstb: Report the correct bank width

gpio: brcmstb: Use bank address as gpiochip label

If the path to the device node is used as gpiochip label then
gpio-brcmstb instances with multiple banks end up with duplicated
names. Instead, use a combination of the driver name with the physical
address of the bank, which is both unique and helpful for devmem
debugging.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>

gpio: mmio: Add DIRECT mode for shared access

The generic MMIO GPIO library uses shadow registers for efficiency,
but this breaks attempts by raspi-gpio to change other GPIOs in the
same bank. Add a DIRECT mode that makes fewer assumptions about the
existing register contents, but note that genuinely simultaneous
accesses are likely to lose updates.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>

gpio: brcmstb: Don't always clear interrupt mask

If the GPIO controller is not being used as an interrupt source
leave the interrupt mask register alone. On BCM2712 it might be used
to generate interrupts to the VPU firmware, and on other devices it
doesn't matter since no interrupts will be generated.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>