HID: core: Fix size as type u32

HID: core: Fix size as type u32

BugLink: http://bugs.launchpad.net/bugs/1773233
commit 6de0b13cc0b4ba10e98a9263d7a83b940720b77a upstream.

When size is negative, calling memset will make segment fault.
Declare the size as type u32 to keep memset safe.

size in struct hid_report is unsigned, fix return type of
hid_report_len to u32.

Cc: stable@vger.kernel.org
Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Acked-by: Khalid Elmously <khalid.elmously@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>