x86: print relevant (tail) part of filename for warnings and crashes

In particular when the origin construct is in a header file (and
hence the file name is an absolute path instead of just the file name
portion) the information can otherwise become rather useless when the
build tree isn't sitting relatively close to the file system root.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>
xen/arm: Add CPU ID for Broadcom Brahma-B15

Let Xen recognize the Broadcom Brahma-B15 CPU by adding the appropriate
MIDR mask to the initialization phase. Further, ensure that the console
output properly reports the CPU manufacturer as "Broadcom Corporation".

Signed-off-by: Marc Carino <marc.ceeeee@gmail.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>