Fix crash in mkimxboot bootloader installation.

mkimxboot requires passing a structure which got extended with another field.
This wasn't adjusted in Rockbox Utility, causing an out of bound access to an
array, which results in a segfault.

Change-Id: I0252849ed0b41f1d8804537c053debc9b0ecd08d

rbutil/mkimxboot/mkimxboot.c

@@ -331,6 +331,9 @@ enum imx_error_t mkimxboot(const char *infile, const char *bootfile,
     const char *outfile, struct imx_option_t opt)
 {
     /* Dump tables */
+    if(opt.fw_variant > VARIANT_COUNT) {
+        return IMX_ERROR;
+    }
     dump_imx_dev_info("[INFO] ");
     /* compute MD5 sum of the file */
     uint8_t file_md5sum[16];

rbutil/rbutilqt/base/bootloaderinstallimx.cpp

@@ -49,6 +49,7 @@ void BootloaderThreadImx::run(void)
     struct imx_option_t opt;
     opt.debug = false;
     opt.output = IMX_DUALBOOT;
+    opt.fw_variant = VARIANT_DEFAULT;
 
     m_error = mkimxboot(m_inputfile.toLocal8Bit().constData(),
             m_bootfile.toLocal8Bit().constData(),