gitignore: add phosphor-dbus-interfaces wrap

The phosphor-dbus-interfaces.wrap file is a redirect due to using
phosphor-logging and shouldn't be checked in.  Add it to the gitignore
to avoid an accidental inclusion.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I28497b00bf8fbbb22651f95bbf20b0d9288ff053
diff --git a/.gitignore b/.gitignore
index 6be2471..b7c3a2c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,6 @@
 build*/*
 subprojects/*
 !subprojects/*.wrap
+subprojects/phosphor-dbus-interfaces.wrap
 !subprojects/.clang-tidy
 !subprojects/.clang-format