arm64: dts: imx8mq-librem5: set debounce interval of volume buttons to 50ms

The default of 5ms is too low.

Signed-off-by: Sebastian Krzyszkowiak <sebastian.krzyszkowiak@puri.sm>
2 jobs for debounce in 63 minutes and 57 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Build
passed #367558
librem5
build:aarch64

00:38:22

passed #367559
librem5:arm64
build:deb

01:03:57