[component] Fix typo for FW_AUTO_ERR_UNKNOWN sonic-net#254

Description
Fixed typo FW_AUTO_ERR_UKNOWN --> FW_AUTO_ERR_UNKNOWN

Motivation and Context
This is a typo and in the interest of a readable code base should not remain. There are also very few references to this as of now so changing it now before more references are added is a priority.

How Has This Been Tested?
Unit tests passing

sonic_platform_base/component_base.py

@@ -12,7 +12,7 @@
 FW_AUTO_SCHEDULED = 3
 FW_AUTO_ERR_BOOT_TYPE = -1
 FW_AUTO_ERR_IMAGE = -2
-FW_AUTO_ERR_UKNOWN = -3
+FW_AUTO_ERR_UNKNOWN = -3
 
 
 class ComponentBase(object):