fix string inconsistencies in callers of panic()

fix string inconsistencies in callers of panic()

panic() (as well as early_panic() in arm) is inconsistently called with or
without a trailing newline.  This results in cases where the lower line of
*****s is not on its own line.

Change panic() to always print a newline itself, and update callers not to.

In addition, panic() was occasionally called with a leading newline, and
occaionally with trailing punctuation which seems rather redundant given the
surrounding context.  Fix up these sitiuations as well.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Tim Deegan <tim@xen.org>
Release-acked-by: George Dunlap <george.dunlap@eu.citrix.com>
Acked-by: Keir Fraser <keir@xen.org>