pata_atiixp: Remove unnecessary parentheses

Clang warns when more than one set of parentheses is used for a
single conditional statement:

drivers/ata/pata_atiixp.c:282:19: warning: equality comparison with
extraneous parentheses [-Wparentheses-equality]
        if((pdev->device == PCI_DEVICE_ID_ATI_IXP600_IDE))
            ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/ata/pata_atiixp.c:282:19: note: remove extraneous parentheses
around the comparison to silence this warning
        if((pdev->device == PCI_DEVICE_ID_ATI_IXP600_IDE))
           ~             ^                              ~
drivers/ata/pata_atiixp.c:282:19: note: use '=' to turn this equality
comparison into an assignment
        if((pdev->device == PCI_DEVICE_ID_ATI_IXP600_IDE))
                         ^~
                         =
1 warning generated.

Reported-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>