arm: linker: fix: incorrect __kernel_ram_start

What is changed?
arch32 related changes in linker script made in commit
ad719014
are reverted.

Why do we need this change?
The main intention of the previous commit was to fix the
broken ci for aarch64.
There was no issue reported for aarch32 and changes were made for
consistency.
However, it looks like keeping the `__kernel_ram_start`
outside of the bss section works differently for different boards.
For fvp_baser_aemv8r arch32, _bss_start points to _rom_region_end and
__kernel_ram_start points to some region between _rom_region_start and
_rom_region_end which leads to test failure.
While for other board like v2m_musca_b1, _bss_start and
__kernel_ram_start are same.
The linker scripts might need a cleanup to avoid issues because of
these inconsistncies however, till we understand this better,
we need to revert this change.

Signed-off-by: Sudan Landge <sudan.landge@arm.com>