x86 boot: simplify pageblock_bits enum declaration

The use of #defines with '##' pre-processor concatenation is a useful
way to form several symbol names with a common pattern.  But when there
is just a single name obtained from that #define, it's just obfuscation.
Better to just write the plain symbol name, as is.

The following patch is a result of my wasting ten minutes looking through
the kernel to figure out what 'PB_migrate_end' meant, and forgetting what
I came to do, by the time I figured out that the #define PB_range macro
defined it.

Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>