nvmecontrol(8): Fix a few mandoc related issues and add a SEE ALSO section

• inserting missing end of block: Ss breaks Bl
• skipping paragraph macro: Pp before Ss
• referenced manual not found: Xr nvme 4 (2 times)
• unknown standard specifier: St The

The macro .St can only be used for standards known by mdoc(7). So add a
SEE ALSO section and add a reference to the NVM Express Base Specification.

MFC after: 2 weeks