cmd/earlyinit: improve error messages

This improves readability, especially on a small display.

Signed-off-by: Ophestra <cat@gensokyo.uk>

cmd/earlyinit/modprobe.go

@@ -26,8 +26,9 @@ var _ report.RepresentableError = ModprobeError{}
 func (ModprobeError) Representable() {}
 func (e ModprobeError) Error() string {
 	return fmt.Sprintf(
-		"modprobe exit status %d: %s",
-		e.ExitCode, strings.TrimSpace(e.Stderr),
+		"%s (exit status %d)",
+		strings.TrimPrefix(strings.TrimSpace(e.Stderr), "modprobe: "),
+		e.ExitCode,
 	)
 }