omap3: CONFIG_REVISION_TAG ifdef check for get_board_rev

Despite being defined with __weak, this declaration of get_board_rev will
conflict with the fallback one when ONFIG_REVISION_TAG is not defined.
Signed-off-by: NPaul Kocialkowski <contact@paulk.fr>
Reviewed-by: NTom Rini <trini@konsulko.com>

arch/arm/cpu/armv7/omap3/sys_info.c

@@ -196,10 +196,12 @@ u32 get_gpmc0_width(void)
  * get_board_rev() - setup to pass kernel board revision information
  * returns:(bit[0-3] sub version, higher bit[7-4] is higher version)
  *************************************************************************/
+#ifdef CONFIG_REVISION_TAG
 u32 __weak get_board_rev(void)
 {
 	return 0x20;
 }
+#endif
 
 /********************************************************
  *  get_base(); get upper addr of current execution