pkey: use unsigned type for bit fields

clang generates a warning:

	../../../../ext/openssl/ossl_pkey.c:326:22: error: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Werror,-Wsingle-bit-bitfield-constant-conversion]
	    arg->interrupted = 1;
	                     ^ ~
	1 error generated.

Author: rhenium

ext/openssl/ossl_pkey.c

@@ -276,9 +276,9 @@ struct pkey_blocking_generate_arg {
     EVP_PKEY_CTX *ctx;
     EVP_PKEY *pkey;
     int state;
-    int yield: 1;
-    int genparam: 1;
-    int interrupted: 1;
+    unsigned int yield: 1;
+    unsigned int genparam: 1;
+    unsigned int interrupted: 1;
 };
 
 static VALUE