net: ethernet: xilinx: cleanup comments

Remove the second 'the'.
Replacements:
endiannes to endianness
areconnected to are connected
Mamagement to Management
undoccumented to undocumented
Xilink to Xilinx
strucutre to structure

Change kernel-doc comment style to c style for
/* Management ...

Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Michal Simek <michal.simek@xilinx.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: David S. Miller <davem@davemloft.net>