ARM: mach-axxia: drop TEXT_OFFSET hack

The Amarillo DTS that we have in the kernel uses a /memreserve/ to
reserve 4 MiB at the start of DRAM. At the same time, it carries a
TEXT_OFFSET hack incrementing it by 3 MiB when targetting the AXXIA
platform. This is inconsistent, and results in the kernel running in
memory that is marked as reserved in the DT.

Now that the decompressor takes /memreserve/ entries into account, and
only requires 2 MiB alignment for the physical to virtual offset of the
kernel direct map, we can simply rely on the decompressor to do the
right thing here, so we no longer need to override TEXT_OFFSET.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>