mfd: tps65090: remove suspend/resume callbacks

The tps65090 mfd driver implement the suspend/resume callbacks
which just disable and enable irqs in suspend/resume respectively.

This operation is already done in irq suspend and irq_resume and
hence it is not require to implement the same in the driver.

Remove this non-require code.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>