UPSTREAM: USB: gadget: zero allocate endpoint 0 buffers

Under some conditions, USB gadget devices can show allocated buffer
contents to a host.  Fix this up by zero-allocating them so that any
extra data will all just be zeros.

Reported-by: Szymon Heidrich <szymon.heidrich@gmail.com>
Tested-by: Szymon Heidrich <szymon.heidrich@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 86ebbc11bb3f60908a51f3e41a17e3f477c2eaa3)
Bug: 210292367
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I72b4376cd4296a8b8af0ade2d702cd420146f3aa
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Issue: FP3SEC-288
(cherry picked from commit 0a638b26)
(cherry picked from commit 5f6ada8bd0b2620b6166176dc6e7769cc368bd21)