ata: sparse fixes for pata_amd.c

drop return statement.
drivers/ata/pata_amd.c:149:2: warning: returning void-valued expression

Commit ce54d161

 pata_amd: update mode selection for NV PATAs

added the initializer for nv_mode_filter but missed deleting the previously
set mode_filter

drivers/ata/pata_amd.c:509:3: warning: Initializer entry defined twice
drivers/ata/pata_amd.c:521:3:   also defined here
drivers/ata/pata_amd.c:544:3: warning: Initializer entry defined twice
drivers/ata/pata_amd.c:556:3:   also defined here

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>