mk: clean up application linker flags
mk: clean up application linker flags

Make some cleaning before fixing the link dependency ordering
in the next commit.

- Move flags for creating a map file in the variable MAPFLAGS.
- Make only one call to linkerprefix macro.
- Group linker flags on the same line.

Signed-off-by: Thomas Monjalon <ee2fa8b2681c737f775687e475dcbf2028a412f1@6wind.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk