arm64: dts: librem5: Limit the max sdio frequency

This is needed for the 1LV Cyress WiFi module to probe correctly.

It also helps improve GNSS sensitivity.

Signed-off-by: Angus Ainslie <angus@akkea.ca>
2 jobs for pureos/byzantium in 69 minutes and 37 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #351319
librem5
build:aarch64

00:54:42

passed #351320
librem5:arm64
build:deb

01:09:37