phy: cpcap-usb: Fix platform_get_irq_byname's error checking.

phy: cpcap-usb: Fix platform_get_irq_byname's error checking.

The platform_get_irq_byname() function returns negative if an error occurs.
zero or positive number on success. platform_get_irq_byname() error
checking for zero is not correct.

Fixes: 0b0e17418a99 ("phy: cpcap-usb: Add CPCAP PMIC USB support")
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>