board: raspberrypi: use regular kernel image

Since release 4.4 a kernel without a trailer is assumed to be device tree
capable. Since our Raspberry Pi defconfigs all use the newer firmware we can
just use the regular kernel image.

https://www.raspberrypi.org/documentation/configuration/device-tree.md

Tested on Raspberry Pi 3.

Cc: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

board/raspberrypi/genimage-raspberrypi.cfg

@@ -9,7 +9,7 @@ image boot.vfat {
       "rpi-firmware/config.txt",
       "rpi-firmware/fixup.dat",
       "rpi-firmware/start.elf",
-      "kernel-marked/zImage"
+      "zImage"
     }
   }
   size = 32M

board/raspberrypi/genimage-raspberrypi0.cfg

@@ -7,7 +7,7 @@ image boot.vfat {
       "rpi-firmware/config.txt",
       "rpi-firmware/fixup.dat",
       "rpi-firmware/start.elf",
-      "kernel-marked/zImage"
+      "zImage"
     }
   }
   size = 32M

board/raspberrypi/genimage-raspberrypi2.cfg

@@ -7,7 +7,7 @@ image boot.vfat {
       "rpi-firmware/config.txt",
       "rpi-firmware/fixup.dat",
       "rpi-firmware/start.elf",
-      "kernel-marked/zImage"
+      "zImage"
     }
   }
   size = 32M

board/raspberrypi/genimage-raspberrypi3.cfg

@@ -8,7 +8,7 @@ image boot.vfat {
       "rpi-firmware/fixup.dat",
       "rpi-firmware/start.elf",
       "rpi-firmware/overlays",
-      "kernel-marked/zImage"
+      "zImage"
     }
   }
   size = 32M