package/libressl: bump to version 2.9.1

package/libressl: bump to version 2.9.1

LibreSSL 2.9.1 now has a test that requires libtls.a, however, when building a
shared library only build, the --disable-static flag is passed to libressl,
which prevents the building of libtls.a.

With libtls.a not being built, the following error occurs:
libressl-2.9.1/tls/.libs/libtls.a', needed by 'handshake_table'.  Stop.

There are three options to fix this:
1) Stick with autotools, and provide a patch that removes building anything in
   the tests folder.
2) Pass --enable-static to LIBRESSL_CONF_OPTS
3) Change the package type to cmake, as a cmake build does not have this issue.

Changing the package type to cmake is the least impactful, it also has the added
benefit of being able to remove the 0001-remove-test-z-DESTDIR-from-ltmain.patch
file.

Signed-off-by: Adam Duskett <Aduskett@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>