usb: musb: da8xx: fix error handling message in probe

We print an error message when platform_device_register_full()
fails, but the initialization of the argument has been removed,
as shown in this warning:

drivers/usb/musb/da8xx.c: In function 'da8xx_probe':
drivers/usb/musb/da8xx.c:521:3: error: 'ret' may be used uninitialized in this function [-Werror=maybe-uninitialized]

This modifies the function to assign the return code before
checking it, and does uses the same method in the check for
usb_phy_generic_register() as well.

Fixes: 947c49af ("usb: musb: da8xx: Remove mach code")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>