service/fsp_srv: Correct returned value in GetGlobalAccessLogMode()

Based off RE, the backing code only ever seems to use 0-2 as the range
of values 1 being a generic log enable, with 2 indicating logging should
go to the SD card. These are used as a set of flags internally.

Given we only care about receiving the log in general, we can just
always signify that we want logging in general.