package/freerdp: fix build with gcc 4.8

Build is broken with gcc 4.8 since bump to version 2.3.1 in commit
01e78811 due to
https://github.com/FreeRDP/FreeRDP/commit/5b2f35747bb37b09b1803b99ca2b1cb248b5bb16

Fixes:
 - http://autobuild.buildroot.org/results/e8e7d43d6183bb6de7bd2c2b300dbdb89f2052d8



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>