Refactor LoadFirmware() to avoid global variables, which don't work when running out of ROM

Review URL: http://codereview.chromium.org/2848006

vboot_firmware/lib/include/vboot_common.h

@@ -55,6 +55,16 @@ int VerifySignatureInside(const void* parent, uint64_t parent_size,
                           const VbSignature* sig);
 
 
+/* Initialize a public key to refer to [key_data]. */
+void PublicKeyInit(VbPublicKey* key, uint8_t* key_data, uint64_t key_size);
+
+
+/* Copy a public key from [src] to [dest].
+ *
+ * Returns 0 if success, non-zero if error. */
+int PublicKeyCopy(VbPublicKey* dest, const VbPublicKey* src);
+
+
 /* Converts a public key to RsaPublicKey format.  The returned key must
  * be freed using RSAPublicKeyFree().
  *