remoteproc: st: Fix sometimes uninitialized ret in st_rproc_probe()

Clang warns (or errors with CONFIG_WERROR=y):

  drivers/remoteproc/st_remoteproc.c:357:6: error: variable 'ret' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
    357 |         if (!ddata->config)
        |             ^~~~~~~~~~~~~~
  drivers/remoteproc/st_remoteproc.c:442:9: note: uninitialized use occurs here
    442 |         return ret;
        |                ^~~
  drivers/remoteproc/st_remoteproc.c:357:2: note: remove the 'if' if its condition is always false
    357 |         if (!ddata->config)
        |         ^~~~~~~~~~~~~~~~~~~
    358 |                 goto free_rproc;
        |                 ~~~~~~~~~~~~~~~
  drivers/remoteproc/st_remoteproc.c:348:9: note: initialize the variable 'ret' to silence this warning
    348 |         int ret, i;
        |                ^
        |                 = 0
  1 error generated.

Set ret to -ENODEV, which seems to be a standard return code when
device_get_match_data() returns NULL.

Closes: https://github.com/ClangBuiltLinux/linux/issues/1944
Fixes: 5c77ebcd

 ("remoteproc: st: Use device_get_match_data()")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lore.kernel.org/r/20231012-st_remoteproc-fix-sometimes-uninit-v1-1-f64d0f2d5b37@kernel.org
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>