powerpc/nvram: Fix an incorrect partition merge

[Michael Ellerman]

On Thu, 2015-10-12 at 07:30:02 UTC, xinhui wrote:
> From: Pan Xinhui <xinhui.pan at linux.vnet.ibm.com>
> 
> When we merge two contiguous partitions whose signatures are marked
> NVRAM_SIG_FREE, We need update prev's length and checksum, then write it
> to nvram, not cur's. So lets fix this mistake now.
> 
> Also use memset instead of strncpy to set the partition's name. It's
> more readable if we want to fill up with duplicate chars .

Does this ever happen in practice? ie. should we backport the fix to stable
kernels?

Has it always been broken?

cheers