vboot-utils: fix RSA redefinition build error with old compilers

Old gcc compilers do not support type redefinitions, which causes a
build failure of the host-vboot-utils package on certain machines. The
vboot-utils source code redefines "typedef struct rsa_st RSA" which is
already defined in the OpenSSL headers.

This commit adds a patch which works around this build issue.

Fixes:

  http://autobuild.buildroot.org/results/1a4/1a45412939a3f9d6fa59d086d834a3b4a4bffef7/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>