bcm47xx: relocate LZMA loader

bcm47xx: relocate LZMA loader

Kernel 5.10 grew bigger than 5.4 so we need to bump BZ_TEXT_START to
allow lzma loader hanel its size.

At the same time BZ_STACK_START needs to be increased to avoid
overwriting the stack.

For a reference see:
d5cf4a5aa4a3 ("brcm47xx: relocate loader to higher address")
2909a4b78e2b ("brcm47xx: relocate the stack in loader")

Cc: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Acked-by: Hauke Mehrtens <hauke@hauke-m.de>