arm64: dts: imx8mq-librem5: remove description of CHG_STATUS_B

That pin is not connected on the board so no need to describe it.
3 jobs for chg_status_b in 107 minutes and 56 seconds (queued for 1 second)
Status Name Job ID Coverage
  Build
passed build:aarch64 #376618
librem5

00:40:00

passed build:deb #376726
librem5:arm64

01:07:55

failed build:deb #376619
librem5:arm64

00:00:00