InputDevice: modernize IDC probe debugging logs

* Use the new-style stream syntax for readability
* Upgrade DEBUGs to INFOs (since the new-style stream syntax filters
  DEBUG logs by default, and since these are hidden behind a
  compile-time constant it's fine to promote them)
* Include the reason we didn't find a particular IDC file

Bug: 365593937
Test: set DEBUG_PROBE to true, check logcat for the InputReader tag
      while connecting an input device
Flag: EXEMPT code disabled by compile-time constant
Change-Id: I7801252b688b4869911792aa66d2dcdceed8713b
diff --git a/include/input/InputDevice.h b/include/input/InputDevice.h
index 7d8c19e..1a48239 100644
--- a/include/input/InputDevice.h
+++ b/include/input/InputDevice.h
@@ -389,6 +389,7 @@
     CONFIGURATION = 0,     /* .idc file */
     KEY_LAYOUT = 1,        /* .kl file */
     KEY_CHARACTER_MAP = 2, /* .kcm file */
+    ftl_last = KEY_CHARACTER_MAP,
 };
 
 /*