msm: pcie: check return value when enabling PCIe GDSC

When enabling GDSC, it is required to check the return value of
the API. Add a proper check and print for the return value.

Change-Id: I4d5a1a660bed6a7f6d72a5d728c36fc54fec7c68
Signed-off-by: Tony Truong <truong@codeaurora.org>