arm: mach-k3: common: Reserve video memory from end of the RAM

arm: mach-k3: common: Reserve video memory from end of the RAM

Setup video memory before page table reservation using
"spl_reserve_video_from_ram_top" which ensures framebuffer memory gets
reserved from the end of RAM.

This is done to enable the next stage to directly skip the
pre-reserved area from previous stage right from the end of RAM without
having to make any gaps/holes to accommodate those regions which was the
case before as previous stage reserved region not from the end of RAM.

Use gd->ram_top instead of local ram_top and update gd->reloc_addr after
each reservation to ensure further regions are reserved properly.

Signed-off-by: Devarsh Thakkar <devarsht@ti.com>
Reviewed-by: Nikhil M Jain <n-jain1@ti.com>