rust: device: Replace CString with CStr in property_present()

The property_present() method expects a &CString currently and will work
only with heap allocated C strings.

In order to make it work with compile-time string constants too, change
the argument type to &CStr.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/e97dcbe0418cc1053fb4bcfac65cc02a0afcdf78.1737005078.git.viresh.kumar@linaro.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>