usb: gadget: bdc: 64-bit pointer capability check

Corrected the register to check the 64-bit pointer
capability state. 64-bit pointer implementation capability
was checking in wrong register, which causes the BDC
enumeration failure in 64-bit memory address.

Fixes: efed421a ("usb: gadget: Add UDC driver for
Broadcom USB3.0 device controller IP BDC")

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Srinath Mannam <srinath.mannam@broadcom.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>