riscv: CONFIG_SPL_FRAMEPOINTER must depend on CONFIG_SPL

The CONFIG_SPL_FRAMEPOINTER symbol is only relevant in SPL.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
Reviewed-by: Ben Dooks <ben.dooks@codethink.co.uk>