diag: Remove BOM in file

This file seems to have a BOM sequence to indicate the file is
UTF-8. There aren't any UTF sequences in the file though, and
this trips up sparse when running on files that include this
header. Remove the BOM so sparse is happy.

Change-Id: Ie25ce60077d1f2b4eb51bf0792635f02d1b33ae7
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>