unified/doc: Update Kernel Primer info for K_ALERT_DEFINE()

Alert section now covers the count limit argument, which was
recently added.

[Part of fix to ZEP-1186]

Change-Id: I8943f42cddf7d39b3e66d02b615c895835bca472
Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
1 file changed