ata: libata: Fix W=1 compilation warning

Commit c494708d ("ata: libata: Cleanup libata-transport")
inadvertently changed the name of the link argument to ata_link in the
kdoc description of ata_tlink_add(), causing warnings to be issue when
compiling with W=1:

drivers/ata/libata-transport.c:690: warning: Function parameter or
struct member 'link' not described in 'ata_tlink_add'
drivers/ata/libata-transport.c:690: warning: Excess function parameter
'ata_link' description in 'ata_tlink_add'

Change the kdoc argument name to "link" to avoid these warnings.

Fixes: c494708d ("ata: libata: Cleanup libata-transport")
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>