mkimxboot: add a switch to force version

Add a switch to override the product and component version of the
sb file. This can usually for target like the Zen X-Fi2 where the
upader allows to drop any file named firmware.sb and prints the
version: by using a funky version the users can check they got it
right. This should not be used on the fuze+ or zenxfi3 because the
OF prevents downgrade.
Also make rbutil always zero out the option structure passed to
mkimxboot, this has already created bugs in the past.

Change-Id: I175c5def52c40c2132e11300e2f037d60a4f040e

rbutil/rbutilqt/base/bootloaderinstallimx.cpp

@@ -47,6 +47,7 @@ void BootloaderThreadImx::run(void)
 {
     qDebug() << "[BootloaderThreadImx] Thread started.";
     struct imx_option_t opt;
+    memset(&opt, 0, sizeof(opt));
     opt.debug = false;
     opt.output = IMX_DUALBOOT;
     opt.fw_variant = VARIANT_DEFAULT;