ath79: fix initramfs boot for Huawei AP5030DN and AP6010DN

ath79: fix initramfs boot for Huawei AP5030DN and AP6010DN

Fix execution of initramfs image on Huawei AP5030DN and AP6010DN by
increasing available memory for LZMA extraction by the loader.

The default leaves only ~23.6 MB between the decompression target
and the running loader code. Extracting images with built-in
packages lead to overwriting the loader code. This causes
the decompression to produce garbage output and hang.

Fix this by overwriting LZMA_TEXT_START to increase the
available memory for LZMA extraction to ~39.6 MB.

Signed-off-by: Marco von Rosenberg <marcovr@selfnet.de>
Link: https://github.com/openwrt/openwrt/pull/22581
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
(cherry picked from commit 17784ad785c2d49c694de332640d85737124eb3a)