fs: erofs: reword "all-fragments" Kconfig text
Currently, both BR2_TARGET_ROOTFS_EROFS_ALL_FRAGMENTS and
BR2_TARGET_ROOTFS_EROFS_FRAGMENTS have the same Kconfig prompt, making
them hard to distinguish.
Reword the one for -Eall-fragments to be distinct.
Signed-off-by: Florian Larysch <fl@n621.de>
Signed-off-by: Julien Olivain <ju.o@free.fr>