arm: rmobile: Remove default value of Kconfig from defconfig
This removes CONFIG_BOOTSTAGE_USER_COUNT, CONFIG_BOOTSTAGE_STASH_ADDR
and CONFIG_BOOTSTAGE_STASH_SIZE from defconfig following boards:
- Alt
- Gose
- Koelsh
- Lager
- Porter
- Silk
- Stout
- Blanche
- Salvator-x
Signed-off-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>