usb: gadget: amd5536udc: remove unnecessary conditions

The condition checking for irq_registered, regs, mem_region and active
are not required as this is the remove function. And we are in the
remove means that probe was successful and they can never be NULL at
this point of code.
It was required in the original code as the remove function was part of
the error handler of probe function.

Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>