clk: gcc: use clk_branch and update halt_flag for PIPE clocks

Move the gate clocks to use clk_branch instead of clk_gate2.
Pipe clocks are sourced from the external PHY, so skip the checking
of the CLK_OFF bit.

Change-Id: I23ef726d5250a8b9e7bd41b77c8d3d356a782202
Signed-off-by: Veera Vegivada <vvegivad@codeaurora.org>