powerpc32/chrp: fix section mismatch warning

This patch fixes a section mismatch warning

WARNING: vmlinux.o(.text+0x213b6): Section mismatch in reference from the function chrp_init_early() to the variable .init.data:boot_command_line
The function chrp_init_early() references
the variable __initdata boot_command_line.
This is often because chrp_init_early lacks a __initdata
annotation or the annotation of boot_command_line is wrong.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>