Reset indentation of this flag. No functional change intended.

Reset indentation of this flag. No functional change intended.
Found with gcc.

sys/dev/ata/chipsets/ata-siliconimage.c: In function 'ata_cmd_ch_attach':
sys/dev/ata/chipsets/ata-siliconimage.c:187:5:
 warning: this 'if' clause does not guard... [-Wmisleading-indentation]
     if (ctlr->chip->cfg2 & SII_INTR)
     ^~
sys/dev/ata/chipsets/ata-siliconimage.c:190:2:
note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
  ch->flags |= ATA_NO_ATAPI_DMA;