am33xx: Unused get_board_rev function removal

All am33xx device tree are using device-tree, so get_board_rev is never actually
called. Thus, we can get rid of it to make the code easier to maintain.

Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
Reviewed-by: Tom Rini <trini@konsulko.com>

arch/arm/cpu/armv7/am33xx/sys_info.c

@@ -51,15 +51,6 @@ u32 get_cpu_type(void)
 }
 
 /**
- * get_board_rev() - setup to pass kernel board revision information
- * returns: 0 for the ATAG REVISION tag value.
- */
-u32 __weak get_board_rev(void)
-{
-	return 0;
-}
-
-/**
  * get_device_type(): tell if GP/HS/EMU/TST
  */
 u32 get_device_type(void)