package/libsrtp: bump version to 1.5.2

Removed patches applied upstream:
https://github.com/cisco/libsrtp/commit/cae277e4377acc90ef787d09ed0d82968bbe809a
https://github.com/cisco/libsrtp/commit/b5fad5f893c7f323a8f8e1c512fa48cf6cdb1c8d



Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>