spmi: pmic_arb: remove ARM build time dependency

Qualcomm PMIC arbiter driver already depends on ARCH_QCOM,
which could be either ARM or ARM64. New version of the PMIC
arbiter controller is available on 64 bit platforms.
Remove ARM dependency to allow driver to be build for 64 bit
platforms.

Signed-off-by: Ivan T. Ivanov <ivan.ivanov@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>