chrp/nvram.c: add MODULE_LICENSE()

chrp/nvram.c: add MODULE_LICENSE()

Add MODULE_LICENSE() to the chrp nvram.c driver to fix the build
warning message:

WARNING: modpost: missing MODULE_LICENSE() in arch/powerpc/platforms/chrp/nvram.o

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>