grub: Use regexp in grub.cfg for smbios product name of rpi4/rpi5

- Latest u-boot has removed smbios model info for raspberrypi devices
- So, grub gets the full product name reported by the firmware (eg.
"Raspberry Pi 4 Model B Rev 1.5" / "Raspberry Pi 5 Model B Rev 1.0")
- We use regexp to be able to support different revisions of the
devices

Signed-off-by: Dimitrios Poulios <dpoulios85@gmail.com>

pkg/grub/rootfs.cfg

@@ -257,10 +257,9 @@ function set_arm64_baremetal {
    fi
    if [ "$smb_vendor" = "raspberrypi" ]; then
       smbios -t 1 -s 5 --set smb_product
-      if [ "$smb_product" = "rpi" ]; then
+      if regexp -- "Raspberry Pi 4 Model B Rev.*" "$smb_product"; then
          set_to_existing_file devicetree /boot/dtb/broadcom/bcm2711-rpi-4-b.dtb
-      elif [ "$smb_product" = "Raspberry Pi 5 Model B Rev 1.0" ]; then
-         #set_to_existing_file devicetree /boot/dtb/broadcom/bcm2712-rpi-5-b.dtb
+      elif regexp -- "Raspberry Pi 5 Model B Rev.*" "$smb_product"; then
          set_global dom0_console "console=ttyAMA10 console=tty1"
       elif [ "$smb_product" = "uno-220" ]; then
          set_to_existing_file devicetree /boot/dtb/broadcom/raspberrypi-uno-220.dtb