If the function platform_get_irq() failed, the negative value
returned will not be detected here. So fix error handling in
tegra_ehci_probe().

Fixes: 79ad3b5a ("usb: host: Add EHCI driver for NVIDIA Tegra SoCs")
Acked-by: NAlan Stern <stern@rowland.harvard.edu>
Acked-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NTang Bin <tangbin@cmss.chinamobile.com>
Link: https://lore.kernel.org/r/20201026090657.49988-1-tangbin@cmss.chinamobile.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>