init: error log on by-name identical replacement

The following message creates unnecessary alarm:

init: Partition system_a already existed in the by-name symlink map \
 with a value of \
 /dev/block/platform/soc/1d84000.ufshc/by-name/system_a, new value \
 /dev/block/platform/soc/1d84000.ufshc/by-name/system_a will be \
 ignored.

and in the code is cited as an ERROR.  The message admittedly does
point out an inefficiency by reporting multiple updates.

Test: compile
Change-Id: I388a76fa078cf9de5840930247f732d16ccb0719