omit drivers fix

Because omit_drivers list use underline always, so when maching with it
the _mod need to be converted as well or sometimes omit-drivers will fail
silently.

Fix this by replace '-' with '_' in instmods function.

Signed-off-by: Dave Young <dyoung@redhat.com>

dracut-functions.sh

@@ -1420,7 +1420,8 @@ instmods() {
                     return $_ret
                 fi
 
-                if [[ $omit_drivers ]] && [[ "$1" =~ $omit_drivers ]]; then
+                _mod=${_mod/-/_}
+                if [[ $omit_drivers ]] && [[ "$_mod" =~ $omit_drivers ]]; then
                     dinfo "Omitting driver ${_mod##$srcmods}"
                     return 0
                 fi