usb: phy: qusb: Remove usage of module params

The values in the module params applies to all the
device instances of the module rather than a single
device. Also, use of module params is not encouraged
on latest kernels. Hence remove the module params
and add the debugfs nodes for each tune registers
to pass the override sequence through the debugfs
files.
While at it remove the code related to emulation PHY
which is not under use anymore.

Change-Id: I634ff2238542242b424fc3d3c200258bbe66bed4
Signed-off-by: Sriharsha Allenki <sallenki@codeaurora.org>