grub, syslinux: add 'nosplash' parameter to mediacheck

features.in/grub/cfg.in/85mediacheck.cfg

 menuentry $"Check this media for defects" --id 'mediachk' {
   echo $"Loading Linux vmlinuz$KFLAVOUR ..."
-  linux$linux_suffix /boot/vmlinuz$KFLAVOUR live @initrd_bootargs@ @stagename@=mediacheck lowmem mediacheck=1 showopts @bootargs@ $EFI_BOOTARGS
+  linux$linux_suffix /boot/vmlinuz$KFLAVOUR live @initrd_bootargs@ @stagename@=mediacheck lowmem mediacheck=1 nosplash showopts @bootargs@ $EFI_BOOTARGS
   echo $"Loading initial ramdisk ..."
   initrd$linux_suffix /boot/@initrd@$KFLAVOUR.@initrd_ext@
 }

features.in/syslinux/cfg.in/85mediacheck.cfg

 label mediachk
   menu label ^Check this media for defects
   kernel /boot/vmlinuz
-  append initrd=/boot/@initrd@ live @initrd_bootargs@ mediacheck=1 stagename=mediacheck showopts lowmem @bootargs@
+  append initrd=/boot/@initrd@ live @initrd_bootargs@ mediacheck=1 stagename=mediacheck nosplash showopts lowmem @bootargs@