common/{hush, kgdb, serial}.c: build by COBJS-$(...) in Makefile

Move global '#ifdef CONFIG_xxx .... #endif' out of the .c files and into
the COBJS-$(CONFIG_xxx) in the Makefile.  Also delete unused var in kgdb
code in the process.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/common/Makefile b/common/Makefile
index 93e3963..f13cd11 100644
--- a/common/Makefile
+++ b/common/Makefile
@@ -35,11 +35,11 @@
 COBJS-y += devices.o
 COBJS-y += dlmalloc.o
 COBJS-y += exports.o
-COBJS-y += hush.o
+COBJS-$(CONFIG_SYS_HUSH_PARSER) += hush.o
 COBJS-y += image.o
 COBJS-y += memsize.o
 COBJS-y += s_record.o
-COBJS-y += serial.o
+COBJS-$(CONFIG_SERIAL_MULTI) += serial.o
 COBJS-y += xyzModem.o
 
 # core command
@@ -144,7 +144,7 @@
 COBJS-$(CONFIG_CMD_DOC) += docecc.o
 COBJS-$(CONFIG_CONSOLE_MUX) += iomux.o
 COBJS-y += flash.o
-COBJS-y += kgdb.o
+COBJS-$(CONFIG_CMD_KGDB) += kgdb.o
 COBJS-$(CONFIG_LCD) += lcd.o
 COBJS-$(CONFIG_LYNXKDI) += lynxkdi.o
 COBJS-$(CONFIG_UPDATE_TFTP) += update.o