Revert "Revert "fbdev: Allow client to request a particular /dev/fbN … #3771

Job	Run time
build (bcmrpi, arm, bcmrpi_defconfig, kernel)	31m 58s
build (arm64, arm64, defconfig, kernel8)	38m 17s
build (bcm2835, arm, bcm2835_defconfig, kernel)	10m 31s
build (bcm2709, arm, bcm2709_defconfig, kernel7)	30m 58s
build (bcm2711, arm64, bcm2711_defconfig, kernel8)	42m 52s
build (bcm2712, arm64, bcm2712_defconfig, kernel_2712)	43m 1s
build (bcm2711_rt, arm64, bcm2711_rt_defconfig, kernel8_rt)	42m 38s
	4h 0m 15s

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