spi: bcm2835: enable shared interrupt support

BCM2711 shares an interrupt betweem 5 SPI interfaces (0, 3, 4, 5 & 6).
Another interrupt is shared between SPI1, SPI2 and UART1, which also
affects BCM2835/6/7. Acting on an interrupt intended for another
interface ought to be harmless (although potentially inefficient), but
it can cause this driver to crash - presumably because some critical
state is not ready.

Add a test to the spi-bcm2835 interrupt service routine that
interrupts are enabled on this interface to avoid the crash and
improve efficiency.

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Link: https://github.com/raspberrypi/linux/issues/5048
Suggested-by: https://github.com/boe-pi
Co-developed-by: Phil Elwell <phil@raspberrypi.com>
Signed-off-by: Phil Elwell <phil@raspberrypi.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Link: https://lore.kernel.org/r/20220719105305.3076354-1-mkl@pengutronix.de
Signed-off-by: Mark Brown <broonie@kernel.org>