Fix these warnings from cppcheck:

hw/display/cirrus_vga.c:2603:
hw/sd/sd.c:348:
hw/timer/exynos4210_mct.c:1033:
target-arm/translate.c:9886:
target-s390x/mem_helper.c:518:
target-unicore32/translate.c:1936:
 style: Consecutive return, break, continue, goto or throw statements are unnecessary.
Signed-off-by: NStefan Weil <sw@weilnetz.de>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NAndreas Färber <afaerber@suse.de>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>