ARM: 8741/1: B15: fix unused label warnings

The new conditionally compiled code leaves some labels and one
variable unreferenced when CONFIG_HOTPLUG_CPU and CONFIG_PM_SLEEP
are disabled:

arch/arm/mm/cache-b15-rac.c: In function 'b15_rac_init':
arch/arm/mm/cache-b15-rac.c:353:1: error: label 'out_unmap' defined but not used [-Werror=unused-label]
 out_unmap:
 ^~~~~~~~~
arch/arm/mm/cache-b15-rac.c:351:1: error: label 'out_cpu_dead' defined but not used [-Werror=unused-label]
 out_cpu_dead:
 ^~~~~~~~~~~~
At top level:
arch/arm/mm/cache-b15-rac.c:53:12: error: 'rac_config0_reg' defined but not used [-Werror=unused-variable]

This replaces the existing #ifdef conditionals with IS_ENABLED()
checks that let the compiler figure out for itself which code to
drop.

Fixes: 55de8877 ("ARM: 8726/1: B15: Add CPU hotplug awareness")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>