arm: kzm9g: Fix undefined reference to `__aeabi_uldivmod' error

arm: kzm9g: Fix undefined reference to `__aeabi_uldivmod' error

The kzm9g board fails in building with -march=armv7-a.
This fixs this problem by converting to do_div().

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USE_PRIVATE_LIBGCC=yes ./MAKEALL kzm9g
...
arch/arm/cpu/armv7/rmobile/librmobile.o: In function `get_time_us':
arch/arm/cpu/armv7/rmobile/timer.c:41: undefined reference to `__aeabi_uldivmod'
arch/arm/cpu/armv7/rmobile/librmobile.o: In function `get_time_ms':
arch/arm/cpu/armv7/rmobile/timer.c:47: undefined reference to `__aeabi_uldivmod'
-----

Signed-off-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>
CC: Tetsuyuki Kobayashi <koba@kmckk.co.jp>