Changed to earlyprintk=efi insteaf of earlyprintk=serial in (U)EFI boot menu entry

This is made possible by the now-available EARLY_PRINTK_EFI kernel parameter.

src/root/config/grub.cfg

@@ -78,7 +78,7 @@ linux  ${kernel} cdroot_hash=${fshash} add_efi_memmap nomodeset gentoo=xfb black
 }
 
 menuentry "[${tag}] Liberté Linux VERSION (Administrator Console)" --class=linux {
-linux  ${kernel} cdroot_hash=${fshash} nomodeset gentoo=nox,root memtest=2 earlyprintk=serial,keep loglevel=6
+linux  ${kernel} cdroot_hash=${fshash} nomodeset gentoo=nox,root memtest=2 earlyprintk=efi loglevel=6
 }