PCI: rockchip: Unindent rockchip_pcie_set_power_limit()

If regulator_get_current_limit() returns 0 or error, return early so the
body of the function doesn't have to be indented as the body of an "if"
statement.  No functional change intended.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>