Fixing doorbell register length to 32bits per spec. On Skylake NTB, the
doorbell registers are 32bit write only registers. The source for the
doorbell is a 64bit register that shows the interrupt bits.
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Fixes: 783dfa6c ("ntb: Adding Skylake Xeon NTB support")
Acked-by: Allen Hubbe <Allen.Hubbe@dell.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>