ipmi: use USEC_PER_SEC instead of 1000000 for more meaningful

Use USEC_PER_SEC instead of 1000000, that making the later bugfix
more clearly.

Signed-off-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --cc drivers/char/ipmi/ipmi_bt_sm.c
Simple merge

diff --cc drivers/char/ipmi/ipmi_kcs_sm.c
Simple merge

diff --cc drivers/char/ipmi/ipmi_smic_sm.c
Simple merge