um: Make GCOV depend on !KCOV

Both do more or less the same thing and are mutually exclusive.
If both are enabled the build will fail.
Sooner or later we can kill UML's GCOV.
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/Kconfig.debug

@@ -16,6 +16,7 @@ config GPROF
 config GCOV
 	bool "Enable gcov support"
 	depends on DEBUG_INFO
+	depends on !KCOV
 	help
 	  This option allows developers to retrieve coverage data from a UML
 	  session.