Drop use of CONFIG_SYS_GENERIC_BOARD in U-Boot

This option is always enabled and is about to be removed. Drop references
to it.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Andreas Bießmann <andreas@biessmann.org>
diff --git a/common/Makefile b/common/Makefile
index 0562d5c..1557a04 100644
--- a/common/Makefile
+++ b/common/Makefile
@@ -26,8 +26,8 @@
 endif
 
 # boards
-obj-$(CONFIG_SYS_GENERIC_BOARD) += board_f.o
-obj-$(CONFIG_SYS_GENERIC_BOARD) += board_r.o
+obj-y += board_f.o
+obj-y += board_r.o
 obj-$(CONFIG_DISPLAY_BOARDINFO) += board_info.o
 obj-$(CONFIG_DISPLAY_BOARDINFO_LATE) += board_info.o