qcom: qpnp-fg-gen3: Continue fg_gen3_probe() when !DEBUG_FS

fg_gen3_probe() should not be dependent on DEBUG_FS
API's returning success. Continue device probe,
when DEBUG_FS is disabled.

Change-Id: I6450ab32a9fac19e46845a8f5b4135289469b3f8
Signed-off-by: Swetha Chikkaboraiah <schikk@codeaurora.org>