package/mmc-utils: add patch to fix build failure

Patch taken from:
 - https://patchwork.kernel.org/patch/10654531/

Fixes:
 - http://autobuild.buildroot.net/results/404bfbd095a7b80273391ea36ea81ba496164b80
 - http://autobuild.buildroot.net/results/233ef5c00951b5be10a59408f4a8781ecc658d74
 - http://autobuild.buildroot.net/results/eba3cf4ac21095bca5af2d5d1d69aca0c9098f9b



Signed-off-by: Sébastien Szymanski <sebastien.szymanski@armadeus.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>