spi: bcm63xx-hsspi: fix error code in probe

This code accidentally returns success instead of a negative error code.

Fixes: 50a6620d ("spi: bcm63xx-hsspi: Add polling mode support")
Signed-off-by: Dan Carpenter <error27@gmail.com>
Reviewed-by: William Zhang <william.zhang@broadcom.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/Y+zmoGH6LubPhiI0@kili


Signed-off-by: Mark Brown <broonie@kernel.org>