usb: isp1760: ignore return value for bus change pattern

usb: isp1760: ignore return value for bus change pattern

We do not care about the return value of that read between the
scratch register write and read, we really just want to make sure that
the pattern in the bus get changed to make sure we are testing
correctly the scratch pattern.

Clang-analyzer complains about the never read scratch variable:
>> drivers/usb/isp1760/isp1760-hcd.c:735:2: warning: Value stored to 'scratch' is never read [clang-analyzer-deadcode.DeadStores]
    scratch = isp1760_hcd_read(hcd, HC_CHIP_ID_HIGH);

Just ignore the return value of that CHIP_ID_HIGH read, add more
information to the comment above why we are doing this. And as at it,
just do a small format change in the error message bellow.

Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Link: https://lore.kernel.org/r/20210819180929.1327349-2-rui.silva@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>