libssh2: fix build failure due to pointer dereferencing ambiguity

libssh2: fix build failure due to pointer dereferencing ambiguity

When dereferencing from *aes_ctr_cipher, being a pointer itself,
ambiguity can occur with compiler and build can fail reporting:
openssl.c:574:20: error: ‘*aes_ctr_cipher’ is a pointer; did you mean to use ‘->’?
     *aes_ctr_cipher->nid = type;

Add a patch to sorround every *aes_ctr_cipher-> occurence with
paranthesis like this (*aes_ctr_cipher)->

Fixes:
http://autobuild.buildroot.net/results/97c/97c43dd2122f55f3166683aa1b29ce1ca54bcb9c/
http://autobuild.buildroot.net/results/4b7/4b728d275f1399e3cb72d40482076ee54b35852a/

Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>