Removing banner when sdcard is removed

Hi , i want to remove banner when no sdcard pushed on my card.
Its showing banner when system boots up , is there any way to remove it ?
how ? how can i change u-boot on my card ? I think its the problem on u-boot inside device.
I need to change u-boot ? serial port access i done before but i m newbie , help please... ?

Dear Kerim,