ARM: 9194/1: assembler: simplify ldr_this_cpu for !SMP builds

When CONFIG_SMP is not defined, the CPU offset is always zero, and so
we can simplify the sequence to load a per-CPU variable.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>