[SPARC]: Re-export saved_command_line to modules.

This reverts some bogosity from the dynamic command-line
changes made on sparc32 and sparc64.

Drivers such as drivers/sbus/char/openprom.c reference
saved_command_line, and can be modular.

The boot_command_line is __initdata, yet the dynamic command-line
changes add modular exports of that symbol, obviously wrong.

Signed-off-by: David S. Miller <davem@davemloft.net>