staging: et131x: Fix variable typo carry_reg1 -> carry_reg2

This mistake was introduced in the patch 'staging: et131x: Convert et1310_address_map.h names from camel case'

Signed-off-by: Mark Einon <mark.einon@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>