configs: rpi_arm64: sync env size with rpi_{3,4}_defconfig

Use the same environment size as the configs dedicated for rpi3 and rpi4.
This allows to switch between the builds and not to loose the settings
stored on the SD card.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Matthias Brugger <mbrugger@suse.com>
diff --git a/configs/rpi_arm64_defconfig b/configs/rpi_arm64_defconfig
index d2406ca..b9bb083 100644
--- a/configs/rpi_arm64_defconfig
+++ b/configs/rpi_arm64_defconfig
@@ -3,6 +3,7 @@
 CONFIG_SYS_TEXT_BASE=0x00080000
 CONFIG_TARGET_RPI_ARM64=y
 CONFIG_SYS_MALLOC_F_LEN=0x2000
+CONFIG_ENV_SIZE=0x4000
 CONFIG_NR_DRAM_BANKS=2
 CONFIG_DISTRO_DEFAULTS=y
 CONFIG_OF_BOARD_SETUP=y