mach-k3: add dynamic mmu fixups for SPL stage

mach-k3: add dynamic mmu fixups for SPL stage

On platforms with spl splash support i.e CONFIG_VIDEO=y, the top of DDR
is reserved for the framebuffer.

The size for the framebuffer is computed at runtime by video_reserve.
During the MMU configuration an entry corresponding to the framebuffer
should be dynamically created to properly map the required space for the
framebuffer.

Therefore this patch adds k3_spl_mem_map_init which adds the required
MMU entry by querying the gd after the framebuffer size has been
computed in spl_reserve_video_from_ram_top.

For non VIDEO=y platforms, the added k3_spl_mem_map_init function gets
optimized out of the final binary so overall, the spl size is not
impacted[1].

[1]: Tested on clang 19.1.7 and gcc 15.1.1

Signed-off-by: Anshul Dalal <anshuld@ti.com>