balena-image-initramfs: raspberrypi4-64: extend initramfs size

The latest layers updates have reached the maximum size. This increase
should not affect existing devices as long as the new kernel plus
initramfs bundle still fits in the existing partitions.

Changelog-entry: extend initramfs size for raspberrypi4-64
Signed-off-by: Alex Gonzalez <alexg@balena.io>

layers/meta-balena-raspberrypi/recipes-core/images/balena-image-initramfs.bbappend

@@ -5,3 +5,4 @@ IMAGE_ROOTFS_MAXSIZE:raspberrypicm4-ioboard-sb = "51200"
 
 # increase initramfs maxsize to 40 MiB
 IMAGE_ROOTFS_MAXSIZE:raspberrypi5 = "40960"
+IMAGE_ROOTFS_MAXSIZE:raspberrypi4-64 = "40960"