arm: Remove unnecessary check on cpu->pmsav7_dregion

Now that we enforce both:
 * pmsav7_dregion == 0 implies has_mpu == false
 * PMSA with has_mpu == false means SCTLR.M cannot be set
we can remove a check on pmsav7_dregion from get_phys_addr_pmsav7(),
because we can only reach this code path if the MPU is enabled
(and so region_translation_disabled() returned false).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 1493122030-32191-8-git-send-email-peter.maydell@linaro.org
