powerpc: Eliminate NULL test and memset after alloc_bootmem

As noted by Akinobu Mita in commit b1fceac2 ("x86: remove unnecessary
memset and NULL check after alloc_bootmem()"), alloc_bootmem and
related functions never return NULL and always return a zeroed region
of memory.  Thus a NULL test or memset after calls to these functions
is unnecessary.

This was fixed using the following semantic patch.
(http://www.emn.fr/x-info/coccinelle/

)

// <smpl>
@@
expression E;
statement S;
@@

E = \(alloc_bootmem\|alloc_bootmem_low\|alloc_bootmem_pages\|alloc_bootmem_low_pages\|alloc_bootmem_node\|alloc_bootmem_low_pages_node\|alloc_bootmem_pages_node\)(...)
... when != E
(
- BUG_ON (E == NULL);
|
- if (E == NULL) S
)

@@
expression E,E1;
@@

E = \(alloc_bootmem\|alloc_bootmem_low\|alloc_bootmem_pages\|alloc_bootmem_low_pages\|alloc_bootmem_node\|alloc_bootmem_low_pages_node\|alloc_bootmem_pages_node\)(...)
... when != E
- memset(E,0,E1);
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Paul Mackerras <paulus@samba.org>