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 bt-dual-amber in 64 minutes and 38 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Build
passed #350522
librem5
build:aarch64

00:42:45

passed #350523
librem5:arm64
build:deb

01:04:38