Comment # 1 on bug 1219593 from Takashi Iwai

The option was disabled on SLE15-SP4, too.  It caused the regression, leading
corruptions of files at building packages (a SLE15-SP4 bug, bsc#1195774).

So, the disablement of CONFIG_READ_ONLY_THP_FOR_FS is intentional, but the
still enabled SLE15-SP5 was rather an overlook.  It should have carried the
config change from SP4, but apparently it didn't happen...