[media] s5p-jpeg: Fix compilation with COMPILE_TEST

ERROR: "__bad_ndelay" [drivers/media/platform/s5p-jpeg/s5p-jpeg.ko] undefined!

That happens because asm-generic doesn't like any ndelay time
bigger than 20us.

Currently, usleep_range() couldn't simply be used, since
exynos4_jpeg_sw_reset() is called with a spinlock held.

So, let's use udelay() instead.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>