arm: Remove RISC OS personality

The RISC OS personality seems to be unused and untested for a long time.
It is doubtful whether this personality worked ever as expected.
Let's rip it out.

Signed-off-by: Richard Weinberger <richard@nod.at>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --cc arch/arm/Kconfig
Simple merge

diff --cc arch/arm/configs/badge4_defconfig
Simple merge

diff --cc arch/arm/kernel/Makefile
Simple merge

diff --cc arch/arm/kernel/arthur.c
Simple merge