HID: intel-ish-hid: avoid bogus uninitialized-variable warning

Older compilers like gcc-4.8 don't see that the variable is
initialized when it is used:

In file included from include/linux/compiler_types.h:68:0,
                 from <command-line>:0:
drivers/hid/intel-ish-hid/ishtp-fw-loader.c: In function 'load_fw_from_host':
include/linux/compiler-gcc.h:75:45: warning: 'fw_info.ldr_capability.max_dma_buf_size' may be used uninitialized in this function [-Wmaybe-uninitialized]
 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
                                             ^
drivers/hid/intel-ish-hid/ishtp-fw-loader.c:770:22: note: 'fw_info.ldr_capability.max_dma_buf_size' was declared here
  struct shim_fw_info fw_info;
                      ^

Make sure to initialize it before returning an error from ish_query_loader_prop().

Fixes: 91b22810

 ("HID: intel-ish-hid: ISH firmware loader client driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>