phy: xgene: remove unsigned integer comparison with less than zero

We get warning with W=1 build:
drivers/phy/phy-xgene.c: In function ‘xgene_phy_xlate’:
drivers/phy/phy-xgene.c:1618:20: warning: comparison of unsigned
expression in ‘< 0’ is always false [-Wtype-limits]
 1618 |  if (args->args[0] < MODE_SATA || args->args[0] >= MODE_MAX) |

args is uint32_t so can never be less than zero, so remove this check

Link: https://lore.kernel.org/r/20200708132809.265967-3-vkoul@kernel.org


Signed-off-by: Vinod Koul <vkoul@kernel.org>