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: I376ccea8b294c47e05b2e67c7da3244582f2d550
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/configure.ac b/configure.ac
index 47931f2..ff8e787 100644
--- a/configure.ac
+++ b/configure.ac
@@ -17,18 +17,8 @@
 AX_APPEND_COMPILE_FLAGS([-Wall -Werror], [CXXFLAGS])
 
 # Checks for libraries.
-PKG_CHECK_MODULES(
-    [SDBUSPLUS],
-    [sdbusplus],
-    [],
-    [AC_MSG_ERROR([The openbmc/sdbusplus package is required])]
-)
-PKG_CHECK_MODULES(
-    [PHOSPHOR_LOGGING],
-    [phosphor-logging],
-    [],
-    [AC_MSG_ERROR([The openbmc/phosphor-logging package is required])]
-)
+PKG_CHECK_MODULES([SDBUSPLUS], [sdbusplus])
+PKG_CHECK_MODULES([PHOSPHOR_LOGGING], [phosphor-logging])
 PKG_CHECK_MODULES(
     [LIBIPMID],
     [libipmid],