board: ti: am62x: evm: Update simple-framebuffer node in device-tree

board: ti: am62x: evm: Update simple-framebuffer node in device-tree

Update simple-framebuffer device-tree node by enumerating framebuffer
related information in existing simple-framebuffer node in Linux
device-tree file and enabling it.

In case there is no simple-framebuffer stub detected in Linux kernel
device-tree and video is still active, then update the device-tree to
reserve the framebuffer region for the active splash screen.

This helps preserve the splash screen till the display server takes over
after OS is booted.

Signed-off-by: Devarsh Thakkar <devarsht@ti.com>