media: platform: synopsys: hdmirx: Fix 64-bit division for 32-bit targets

The build fails for 32-bit targets with:

  arm-linux-gnueabi-ld: drivers/media/platform/synopsys/hdmirx/snps_hdmirx.o: in function `hdmirx_get_timings':
  snps_hdmirx.c:(.text.hdmirx_get_timings+0x46c): undefined reference to `__aeabi_uldivmod'

bt->pixelclock is __u64, which causes the compiler to emit a libcall for
64-bit division. Use the optimized kernel helper, div_u64(), to resolve
this.

Fixes: 7b59b132 ("media: platform: synopsys: Add support for HDMI input driver")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>