clk: qcom: gcc-sm8150: Use ALWAYS_ON flag as a workaround for emac gdsc

emac GDSC currently has issues (seen on SA8155p-ADP) when its
turn'ed ON, once its already in OFF state. So when the 'eth'
interface is turned up, it fails (as RGMII CLK is unavailable,
which is gated by emac GDSC) with the following logs:

  qcom-ethqos 20000.ethernet eth0: PHY [stmmac-0:07] driver [Micrel
                                   KSZ9031 Gigabit PHY] (irq=150)
  <..snip..>
  qcom-ethqos 20000.ethernet: Failed to reset the dma
  qcom-ethqos 20000.ethernet eth0: stmmac_hw_setup: DMA engine
                                   initialization failed
  qcom-ethqos 20000.ethernet eth0: stmmac_open: Hw setup failed

So, use the 'ALWAYS_ON' flag as a workaround to describe emac GDSC
for now.

Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Bhupesh Sharma <bhupesh.sharma@linaro.org>