usb: dwc3: make maximum-speed a per-instance attribute

in order to allow different instances of the
core work in different maximum speeds, we will
move the maximum_speed module_parameter to
both DeviceTree (making use the new maximum-speed
DT property) and platform_data.

Signed-off-by: Felipe Balbi <balbi@ti.com>
Change-Id: I5f6c8358db001cef527dd35e83b3e1ea91bfa38f
Git-commit: f7e846f0956917888b28b52726ee8779a39d84b6
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[vvreddy@codeaurora.org: resolved merge conflicts]
Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>