spi: spi-pxa2xx: Check status register to determine if SSSR_TINT is disabled

On Intel Baytrail, there is case when interrupt handler get called, no SPI
message is captured. The RX FIFO is indeed empty when RX timeout pending
interrupt (SSSR_TINT) happens.

Use the BIOS version where both HSUART and SPI are on the same IRQ. Both
drivers are using IRQF_SHARED when calling the request_irq function. When
running two separate and independent SPI and HSUART application that
generate data traffic on both components, user will see messages like
below on the console:

  pxa2xx-spi pxa2xx-spi.0: bad message state in interrupt handler

This commit will fix this by first checking Receiver Time-out Interrupt,
if it is disabled, ignore the request and return without servicing.

Signed-off-by: Tan, Jui Nee <jui.nee.tan@intel.com>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org