core/linux-rpi: update $pkgbase.install

Fix syntax for /etc/fstab check and run it in post_install to cover users coming
from linux-aarch64

core/linux-rpi/linux-rpi.install

@@ -11,13 +11,16 @@ correct_fstab() {
   # starting with v5.10.y, fstab requires a padded zero in the path to /boot
   if [[ -f /etc/fstab ]]; then
     if grep -q mmcblk1p1 /etc/fstab; then
-      sed -i 's/mmcblk1p1/mmcblk01p1/' /etc/fstab
+      sed -i 's/mmcblk1p1/mmcblk0p1/' /etc/fstab
     fi
   fi
 }
 
 post_install () {
   disable_cma
+
+  # coming from linux-aarch64 also needs a padded zero in the path to /boot
+  correct_fstab
 }
 
 post_upgrade() {