ata: use COMMAND_LINE_SIZE for ata_force_param_buf[] size

Use COMMAND_LINE_SIZE instead PAGE_SIZE for ata_force_param_buf[]
size as libata parameters buffer doesn't need to be bigger than
the command line buffer.

For many architectures this results in decreased libata-core.o
size (COMMAND_LINE_SIZE varies from 256 to 4096 while the minimum
PAGE_SIZE is 4096).

Code size savings on m68k arch using (modified) atari_defconfig:

   text    data     bss     dec     hex filename
before:
  41064    4413      40   45517    b1cd drivers/ata/libata-core.o
after:
  41064     573      40   41677    a2cd drivers/ata/libata-core.o

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>