hard-coded u-boot load addresses fragile and breaking low-memory boards

https://github.com/armbian/build/blob/0e7fc1c8e0470e75c4b375dfdf0e8912e47da283/config/bootscripts/boot-meson64.cmd#L7

Compare values to u-boot config:

```
#define BOOTM_SIZE __stringify(0x1700000)
#define KERNEL_ADDR_R __stringify(0x08080000)
#define KERNEL_COMP_ADDR_R __stringify(0x0d080000)
#define FDT_ADDR_R __stringify(0x08008000)
#define SCRIPT_ADDR_R __stringify(0x08000000)
#define PXEFILE_ADDR_R __stringify(0x01080000)
#define FDTOVERLAY_ADDR_R __stringify(0x01000000)
#define RAMDISK_ADDR_R __stringify(0x13000000)
```

La Frite will not boot Armbian now that some additional reserved memory regions exist, these do not conflict with the defaults built into U-boot (confirmed on my side). Suggest removing these Armbian-sourced values as default and any board that can't boot normally should put these in armbianEnv.txt or otherwise handle them in a board-specific manner

Start with config/bootscripts/boot-meson64.cmd at line 7 and compare its load-address values with the listed U-Boot defaults. Inspect how board-specific armbianEnv.txt handling is represented in this repository, then verify that removing the Armbian defaults preserves boot behavior for affected boards, including La Frite.

Written by the indexing model from the issue text.