boards: nxp: frdm_mcxn947: fix debug access to secure RAM and peripherals

By default, LinkServer's memory map for the MCXN947 does not define
memory regions for the SRAM or peripheral bus in secure mode. This
results in gdb failing to read from these memory regions unless
explicitly told ignore the debugger memory map via
"set mem inaccessible-by-default off".

To resolve this, define memory regions for SRAM and peripherals in
secure mode via the commandline arguments passed to LinkServer in
board.cmake.

Signed-off-by: Daniel DeGrasse <daniel.degrasse@nxp.com>