ARM: EXYNOS: Remove "linux/bug.h" from pmu.c

This patch removes unnecessary header file inclusion from pmu.c.

Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>