fix(dracut-functions): avoid awk in get_maj_min()

The `get_maj_min()` cache lookup is commonly used
across many flows. While `awk` should be available,
some highly constrained environments may not have it.
A second call to `grep` can provide the same behaviour
without adding a dependnecy.

Lines in the cache will be of the form "/dev/sda2 8:2".
`awk '{print $NF}'` returns the last word of a matching line. Since
the initial matching regex is so specific a second call to grep can
easily extract the last word.

(cherry picked commit ec7efd5)

Related: RHEL-47145

dracut-functions.sh

@@ -243,7 +243,7 @@ get_maj_min() {
     local _out
 
     if [[ $get_maj_min_cache_file ]]; then
-        _out="$(grep -m1 -oE "^${1//\\/\\\\} \S+$" "$get_maj_min_cache_file" | awk '{print $NF}')"
+        _out="$(grep -m1 -oE "^${1//\\/\\\\} \S+$" "$get_maj_min_cache_file" | grep -oE "\S+$")"
     fi
 
     if ! [[ "$_out" ]]; then