drivers/hsi/controllers/omap_ssi{,_port}.c: fix failure checks

1.

[linux-3.16-rc5/drivers/hsi/controllers/omap_ssi.c:357]: (style) Checking if
unsigned variable 'gdd_irq' is less than zero.

Source code is

    omap_ssi->gdd_irq = platform_get_irq_byname(pd, "gdd_mpu");
    if (omap_ssi->gdd_irq < 0) {

2.

[linux-3.16-rc5/drivers/hsi/controllers/omap_ssi_port.c:1017]: (style) Checking
if unsigned variable 'irq' is less than zero.

Source code is

    omap_port->irq = platform_get_irq(pd, 0);
    if (omap_port->irq < 0) {

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=80441


Reported-by: David Binderman <dcb314@hotmail.com>
Signed-off-by: Andrey Utkin <andrey.krieger.utkin@gmail.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>