of/sparc: remove include of linux/of_platform.h from asm/of_platform.h

Now that we have removed all inclusions of asm/of_platform.h, this
compatability include can be removed.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>