Update hmm text for mgrep.

mgrep also scans *.bp files.

Test: hmm
Change-Id: Ie7bf79d42958b269f4d2fb55d7728a22a52bf908
diff --git a/envsetup.sh b/envsetup.sh
index 9e381a2..5292d38 100644
--- a/envsetup.sh
+++ b/envsetup.sh
@@ -22,7 +22,7 @@
 - jgrep:      Greps on all local Java files.
 - resgrep:    Greps on all local res/*.xml files.
 - mangrep:    Greps on all local AndroidManifest.xml files.
-- mgrep:      Greps on all local Makefiles files.
+- mgrep:      Greps on all local Makefiles and *.bp files.
 - sepgrep:    Greps on all local sepolicy files.
 - sgrep:      Greps on all local source files.
 - godir:      Go to the directory containing a file.