Cisco 7912 firmware not recognized - fix provided, please manage and commit

[evazzoler]

Hi,
cisco 7912 firmware file extension is ".sbin" and not ".sbn", so its filename generates a "not found" and red background in the web interface.
In Sccp_manager.class.php, please change row 2117

from:
$file_ext = array('.loads', '.sbn', '.bin', '.zup');

to:
$file_ext = array('.loads', '.sbn', '.bin', '.zup', '.sbin');