mce-intel-p4-p6: prevent build errors with -Werror=format-security

mce-intel-p4-p6: prevent build errors with -Werror=format-security

On Fedora, -Werror=format-security is now used on packages, with
causes the following build error:

mce-intel-p4-p6.c: In function 'p4_decode_model':
mce-intel-p4-p6.c:130:4: error: format not a string literal and no format arguments [-Werror=format-security]
    mce_snprintf(e->error_msg, p4_model[i].str);
    ^~~~~~~~~~~~
cc1: some warnings being treated as errors

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>