scripts: Fix typo in headers_install.sh

This patch fixes a spelling typo in scripts/headers_install.sh
Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/headers_install.sh

@@ -11,7 +11,7 @@ then
 	echo "asm/inline/volatile keywords."
 	echo
 	echo "INFILE: header file to operate on"
-	echo "OUTFILE: output file which the processed header is writen to"
+	echo "OUTFILE: output file which the processed header is written to"
 
 	exit 1
 fi