configure: Fix typo of the have_afalg variable

The variable is called 'have_afalg' and not 'hava_afalg'.

Fixes: f0d92b56 ('introduce some common functions for af_alg backend')
Message-Id: <20200203160046.23194-1-thuth@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: NLongpeng(Mike) <longpeng2@huawei.com>
Signed-off-by: NThomas Huth <thuth@redhat.com>

configure

@@ -5843,7 +5843,7 @@ fi
 
 ##########################################
 # check for usable AF_ALG environment
-hava_afalg=no
+have_afalg=no
 cat > $TMPC << EOF
 #include <errno.h>
 #include <sys/types.h>