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: NPaul Kocialkowski <contact@paulk.fr>
Reviewed-by: NTom Rini <trini@konsulko.com>

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

@@ -50,15 +50,6 @@ u32 get_cpu_type(void)
 	return partnum;
 }
 
-/**
- * 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
  */