usb: host: ehci-exynos: Fix error check in exynos_ehci_probe()

If the function platform_get_irq() failed, the negative value
returned will not be detected here. So fix error handling in
exynos_ehci_probe(). And when get irq failed, the function
platform_get_irq() logs an error message, so remove redundant
message here.

Fixes: 1bcc5aa8

 ("USB: Add initial S5P EHCI driver")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Zhang Shengju <zhangshengju@cmss.chinamobile.com>
Signed-off-by: Tang Bin <tangbin@cmss.chinamobile.com>
Link: https://lore.kernel.org/r/20200602114708.28620-1-tangbin@cmss.chinamobile.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>