ARM: fix CONFIG_VIRT_TO_BUS handling

887cbce0 "arch Kconfig: centralise CONFIG_ARCH_NO_VIRT_TO_BUS"
and  4febd95a "Select VIRT_TO_BUS directly where needed" from
Stephen Rothwell changed globally how CONFIG_VIRT_TO_BUS is
selected, while my own a5d533ee

 "ARM: disable virt_to_bus/
virt_to_bus almost everywhere" was merged at the same time and
changed which platforms select it on ARM.

The result of this conflict was that we again see CONFIG_VIRT_TO_BUS
on all ARM systems. This patch fixes up the problem and removes
CONFIG_ARCH_NO_VIRT_TO_BUS again on ARM.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>