build: pkg anti-pattern: use defaults

Use the defaults in the pkg check where the default error message is
sufficient to identify which package is missing.

Change-Id: Id77ae17d8977c5aaa01b33325c57a73391f980c2
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/configure.ac b/configure.ac
index 66ee856..5895956 100644
--- a/configure.ac
+++ b/configure.ac
@@ -14,10 +14,8 @@
     [AC_SUBST([PYTHON], [echo "$PYTHON"])],
     [AC_MSG_ERROR([Could not find python-2.7 installed...python-2.7 is required])])
 
-PKG_CHECK_MODULES([SDBUSPLUS], [sdbusplus],,\
-    AC_MSG_ERROR(["Requires sdbusplus package."]))
-PKG_CHECK_MODULES([PHOSPHOR_LOGGING], [phosphor-logging],,\
-    AC_MSG_ERROR(["Requires phosphor-logging package."]))
+PKG_CHECK_MODULES([SDBUSPLUS], [sdbusplus])
+PKG_CHECK_MODULES([PHOSPHOR_LOGGING], [phosphor-logging])
 
 # Suppress the --with-libtool-sysroot error
 LT_INIT