bootm: Update bootm_process_cmdline_env() to use flags

At present only one transformation is supported: making the Linux console
silent. To prepare for adding more, convert the boolean parameter into a
flag value.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/test/bootm.c b/test/bootm.c
index c203f0a..ba08920 100644
--- a/test/bootm.c
+++ b/test/bootm.c
@@ -23,26 +23,26 @@
 	/* 'silent_linux' not set should do nothing */
 	env_set("silent_linux", NULL);
 	env_set("bootargs", CONSOLE_STR);
-	ut_assertok(bootm_process_cmdline_env(true));
+	ut_assertok(bootm_process_cmdline_env(BOOTM_CL_SILENT));
 	ut_asserteq_str(CONSOLE_STR, env_get("bootargs"));
 
 	env_set("bootargs", NULL);
-	ut_assertok(bootm_process_cmdline_env(true));
+	ut_assertok(bootm_process_cmdline_env(BOOTM_CL_SILENT));
 	ut_assertnull(env_get("bootargs"));
 
 	ut_assertok(env_set("silent_linux", "no"));
 	env_set("bootargs", CONSOLE_STR);
-	ut_assertok(bootm_process_cmdline_env(true));
+	ut_assertok(bootm_process_cmdline_env(BOOTM_CL_SILENT));
 	ut_asserteq_str(CONSOLE_STR, env_get("bootargs"));
 
 	ut_assertok(env_set("silent_linux", "yes"));
 	env_set("bootargs", CONSOLE_STR);
-	ut_assertok(bootm_process_cmdline_env(true));
+	ut_assertok(bootm_process_cmdline_env(BOOTM_CL_SILENT));
 	ut_asserteq_str("console=", env_get("bootargs"));
 
 	/* Empty buffer should still add the string */
 	env_set("bootargs", NULL);
-	ut_assertok(bootm_process_cmdline_env(true));
+	ut_assertok(bootm_process_cmdline_env(BOOTM_CL_SILENT));
 	ut_asserteq_str("console=", env_get("bootargs"));
 
 	return 0;