common: cmd_sata: Fix usage text for 'sata init'

common: cmd_sata: Fix usage text for 'sata init'

Currently sata usage text prints a double 'sata' for the init command.

MX53LOCO U-Boot > sata
sata - SATA sub system

Usage:
sata sata init - init SATA sub system
sata info - show available SATA devices
sata device [dev] - show or set current device
sata part [dev] - print partition table
sata read addr blk# cnt
sata write addr blk# cnt

Remove the extra 'sata' from the 'sata init' line.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>