arm64: dts: librem5-devkit: Hog speaker-mute GPIO

This makes sure the handset speaker is on.
2 jobs for next-devkit in 62 minutes and 9 seconds
Status Name Job ID Coverage
  Build
failed build:aarch64 #327549
librem5 allowed to fail

00:14:19

passed build:deb #327550
librem5:arm64

01:02:09

 
Name Stage Failure
failed
build:aarch64 Build
  LD [M]  drivers/bluetooth/hci_uart.o
CC [M] drivers/hid/hid-sensor-custom.o
LD [M] drivers/hid/hid-picolcd.o
LD [M] drivers/hid/hid-uclogic.o
LD [M] drivers/hid/wacom.o
LD [M] drivers/hid/hid-wiimote.o
AR drivers/hid/built-in.a
AR drivers/built-in.a
ERROR: Job failed: exit code 1