arm: dts: bcm2711-rpi-4-b: Adds buttons for speaker profile

arm: dts: bcm2711-rpi-4-b: Adds buttons for speaker profile

Tizen Speaker Profile uses a keypad that consists of 5 buttons for
up/down/left/right/center. The buttons are connected to GPIO pins as
follows.

GPIO16 : KEY_VOLUMEUP
GPIO13 : KEY_VOLUMEDOWN
GPIO6 : KEY_FASTFORWARD
GPIO12 : KEY_REWIND
GPIO25 : KEY_PLAYPAUSE

Signed-off-by: Jaechul Lee <jcsing.lee@samsung.com>
 Conflicts:
	arch/arm/boot/dts/bcm2711-rpi-4-b.dts

Change-Id: I25bffde7c669c0572496ec3adbd4240fb2ed49cd
Signed-off-by: Hoegeun Kwon <hoegeun.kwon@samsung.com>