soc: qcom: gsbi: Fix error handling in gsbi_probe()

If of_platform_populate() fails in gsbi_probe(),
gsbi->hclk is left undisabled.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>