dmaengine: idxd: Use cpu_feature_enabled()

When testing x86 feature bits, use cpu_feature_enabled() so that
build-disabled features can remain off, regardless of what CPUID says.

Fixes: 8e50d392

 ("dmaengine: idxd: Add shared workqueue support")
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-By: Vinod Koul <vkoul@kernel.org>
Cc: <stable@vger.kernel.org>