[ARC] GDBServer: Fix debug print for big endian

This may give funny results when len==3, but at least this works OK
for both endiannesses when len=={1, 2, 4}.

Signed-off-by: Mischa Jonker <mjonker@synopsys.com>
Signed-off-by: Anton Kolesov <akolesov@synopsys.com>