UPSTREAM: PCI/ASPM: Remove redundant check of pcie_set_clkpm

UPSTREAM: PCI/ASPM: Remove redundant check of pcie_set_clkpm

Without supporting clock PM capable, if we want to disable
clkpm, we don't need this extra check as it already be zero for
the enable argument. And it's the same for enabling clkpm here.
So let's remove this check.

Change-Id: I0dc251e5dea940a2288fbb31a58336dea83f2515
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
(cherry picked from git.kernel.org/cgit/linux/kernel/git/next/linux-next.git
commit a6c1c6f3547b6c4cbd4a30d67a968ee1519a8ffd)