mbedtls: fix API compatibility

Add upstream patch fixing API compatibility with previous releases.

Fixes (hiawatha):
http://autobuild.buildroot.net/results/ce6/ce6b4a50e6aafd06f82eaae688dd8720b982e9c2/
http://autobuild.buildroot.net/results/cde/cdec7ae3565d5b76a9bc50156c6244b44197534e/
http://autobuild.buildroot.net/results/9c1/9c1aec09c03f60bee9dc134da5a29e2671fc3b5e/



Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>