tools: logos: Rename TI logo files

Change the file name from ti.gz and ti.bmp to ti_logos_414x97_32bpp to
help user understand the resolution and identify the logo files when
placed in the boot partition and update the splashfile name with the
same in .env file.

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