phy: qcom-qmp: Fix phy pipe clock gating

Pipe clock comes out of the phy and is available as long as
the phy is turned on. Clock controller fails to gate this
clock after the phy is turned off and generates a warning.

/ # [   33.048561] gcc_usb3_phy_pipe_clk status stuck at 'on'
[   33.048585] ------------[ cut here ]------------
[   33.052621] WARNING: CPU: 1 PID: 18 at ../drivers/clk/qcom/clk-branch.c:97 clk_branch_wait+0xf0/0x108
[   33.057384] Modules linked in:
[   33.066497] CPU: 1 PID: 18 Comm: kworker/1:0 Tainted: G        W       4.12.0-rc7-00024-gfe926e34c36d-dirty #96
[   33.069451] Hardware name: Qualcomm Technologies, Inc. DB820c (DT)
...
[   33.278565] [<ffff00000849b27c>] clk_branch_wait+0xf0/0x108
[   33.286375] [<ffff00000849b2f4>] clk_branch2_disable+0x28/0x34
[   33.291761] [<ffff0000084868dc>] clk_core_disable+0x5c/0x88
[   33.297660] [<ffff000008487d68>] clk_core_disable_lock+0x20/0x34
[   33.303129] [<ffff000008487d98>] clk_disable+0x1c/0x24
[   33.309384] [<ffff0000083ccd78>] qcom_qmp_phy_poweroff+0x20/0x48
[   33.314328] [<ffff0000083c53f4>] phy_power_off+0x80/0xdc
[   33.320492] [<ffff00000875c950>] dwc3_core_exit+0x94/0xa0
[   33.325784] [<ffff00000875c9ac>] dwc3_suspend_common+0x50/0x60
[   33.331080] [<ffff00000875ca04>] dwc3_runtime_suspend+0x48/0x6c
[   33.336810] [<ffff0000085b82f4>] pm_generic_runtime_suspend+0x28/0x38
[   33.342627] [<ffff0000085bace0>] __rpm_callback+0x150/0x254
[   33.349222] [<ffff0000085bae08>] rpm_callback+0x24/0x78
[   33.354604] [<ffff0000085b9fd8>] rpm_suspend+0xe0/0x4e4
[   33.359813] [<ffff0000085bb784>] pm_runtime_work+0xdc/0xf0
[   33.365028] [<ffff0000080d7b30>] process_one_work+0x12c/0x28c
[   33.370576] [<ffff0000080d7ce8>] worker_thread+0x58/0x3b8
[   33.376393] [<ffff0000080dd4a8>] kthread+0x100/0x12c
[   33.381776] [<ffff0000080836c0>] ret_from_fork+0x10/0x50

Fix this by disabling it as the first thing in phy_exit().

Fixes: e78f3d15 ("phy: qcom-qmp: new qmp phy driver for qcom-chipsets")
Signed-off-by: Vivek Gautam <vivek.gautam@codeaurora.org>
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>