u-boot_%.bbappend: Increase CONFIG_SYS_BOOTM_LEN

Increase CONFIG_SYS_BOOTM_LEN for machine raspberrypi4 (32-bit)
because the kernel size has increased. This fixes the following
issue when booting an image with U-Boot:

   Image Name:   Linux-6.6.63-v7l
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    8559752 Bytes = 8.2 MiB
   Load Address: 00008000
   Entry Point:  00008000
   Verifying Checksum ... OK
   Booting using the fdt blob at 0x2eff2000
Working FDT set to 2eff2000
   Loading Kernel Image to 8000
Image too large: increase CONFIG_SYS_BOOTM_LEN
Must RESET board to recover

Fixes: https://github.com/agherzan/meta-raspberrypi/issues/1306

Signed-off-by: Leon Anavi <leon.anavi@konsulko.com>

recipes-bsp/u-boot/files/maxsize.cfg

@@ -0,0 +1 @@
+CONFIG_SYS_BOOTM_LEN=0x1000000

recipes-bsp/u-boot/u-boot_%.bbappend

@@ -5,6 +5,7 @@ SRC_URI:append:rpi = " \
 "
 
 SRC_URI:append:rpi = " file://0001-rpi-always-set-fdt_addr-with-firmware-provided-FDT-address.patch"
+SRC_URI:append:raspberrypi4 = " file://maxsize.cfg"
 
 DEPENDS:append:rpi = " u-boot-default-script"