ipmi_ssif: Rename idle state and check

[ Upstream commit 8230831c43a328c2be6d28c65d3f77e14c59986b ]

Rename the SSIF_IDLE() to IS_SSIF_IDLE(), since that is more clear, and
rename SSIF_NORMAL to SSIF_IDLE, since that's more accurate.

Cc: stable@vger.kernel.org
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Stable-dep-of: 6d2555cde291 ("ipmi: fix SSIF not responding under certain cond.")
Signed-off-by: Sasha Levin <sashal@kernel.org>