ath11k: pci: remove unnecessary mask in ath11k_pci_enable_ltssm()

0x10 is a leftover and unnecessary, GCC_GCC_PCIE_HOT_RST_VAL is already defined
to 0x10.

No functional changes, compile tested only.

Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1608143051-5386-1-git-send-email-kvalo@codeaurora.org