configs: Increase malloc size after relocation

configs: Increase malloc size after relocation

Current default size of 0x100000 is not capable of getting the FIT
buffer during boot when transitioning to using binman generated boot
images for certain K3 devices, so increase it to 0x400000. Since A72 SPL
is coming after relocation to DDR this should not be an issue for any K3
device, so make it default for all.

Signed-off-by: Neha Malcom Francis <n-francis@ti.com>
Acked-by: Andrew Davis <afd@ti.com>