imx8: mek: move HUSH_PARSER to defconfig

imx8: mek: move HUSH_PARSER to defconfig

Move HUSH_PARSER to defconfig, otherwise meet
"
=> run netboot
Booting from net ...
Unknown command 'if' - try 'help'
Unknown command 'then' - try 'help'
Unknown command 'else' - try 'help'
Unknown command 'fi' - try 'help'
Unknown command '0x80280000' - try 'help'
Unknown command 'if' - try 'help'
Unknown command 'then' - try 'help'
Unknown command 'then' - try 'help'
Unknown command 'else' - try 'help'
Unknown command 'fi' - try 'help'
Unknown command 'else' - try 'help'
Unknown command 'fi' - try 'help'
"

Signed-off-by: Peng Fan <peng.fan@nxp.com>