The linker script has no board-specific information that necessitates it
having a name derived from the board name. Give it a fixed name, so we
can later reuse the same linker script for multiple boards.

Change-Id: Ie6650f00389f4ab8577ae82a36c620af9c64101e
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>