kern: Include function name on debug and error print functions

kern: Include function name on debug and error print functions

With the following change, we see standard (grub_dprintf) and
error (grub_error) logs with the function name embedded (see below)
into the log which is particular useful when debugging:

  commands/efi/tpm.c:grub_tpm_measure:281:tpm: log_event, pcr = 8, size = 0xb,

Including one more field on the print log impacts the binary sizes
and in turn their respective distro packages. For Fedora rpm packages
the increase is 20k approximately.

Signed-off-by: Leo Sandoval <lsandova@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>