The config MV64X60 in arch/powerpc/platforms/embedded6xx/Kconfig is non-prompt selected nowhere -- thus, cannot be enabled. In addition, a few other configs cannot be enabled due to their dependency on MV64X60, e.g., EDAC_MV64X60. The last to use this driver was by PrPMC 280/2800, for which the support was ended with the commit 3c8464a9b12b ("powerpc: Delete old PrPMC 280/2800 support"). This looks like the related configs (e.g., MV64X60, EDAC_MV64X60) and the code (e.g., drivers/edac/mv64x60_edac.c) for Marvell MV64X60 MPSC are now obsolete.
https://git.kernel.org/pub/scm/linux/kernel/git/ras/ras.git/commit/?h=edac-drivers&id=0385979a30dc4abdef2dcebbccef818947c80cb7
https://github.com/linuxppc/linux/commit/a329ddd472fa2af0c19a73b8658898ae7fd658ad https://github.com/linuxppc/linux/commit/600cc3c9c62defd920da07bc585eb739247bb732 https://patchwork.kernel.org/project/linux-watchdog/patch/9c2952bcfaec3b1789909eaa36bbce2afbfab7ab.1616085654.git.christophe.leroy@csgroup.eu/
The watchdog patch is flagged 'accepted' in patchwork, should go into 5.14
The watchdog driver was removed in: bc65baf73b68 ("watchdog: Remove MV64x60 watchdog driver")