GP tests: delete CFG_GP_TESTSUITE_ENABLE

The two Makefile variables: CFG_GP_TESTSUITE_ENABLE and
CFG_GP_PACKAGE_PATH are redundant, since when the test suite is enabled
one has to provide the path to the package. This patch also consolidates
CFLAGS so that WITH_GP_TESTS is used everywhere instead of
XTEST_WITH_GP_TESTS and CFG_GP_TESTSUITE_ENABLE.

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Pascal Brand <pascal.brand@linaro.org>
diff --git a/Makefile b/Makefile
index 91dee97..ed60d48 100644
--- a/Makefile
+++ b/Makefile
@@ -36,7 +36,7 @@
 
 .PHONY: patch
 patch:
-ifeq ($(CFG_GP_TESTSUITE_ENABLE),y)
+ifdef CFG_GP_PACKAGE_PATH
 CFG_GP_API?=1.0
 CFG_GP_XSL_PACKAGE_PATH?=$(CURDIR)/package/testsuite/global_platform/api_1.0/GP_XSL_TEE_Initial_Configuration-Test_Suite_v1_0_0-2014-12-03-STM
 
@@ -254,5 +254,5 @@
 
 else
 patch:
-	$(q) echo "Please define CFG_GP_TESTSUITE_ENABLE=y" && false
+	$(q) echo "Please define CFG_GP_PACKAGE_PATH" && false
 endif