powerpc: Typo s/use use/use/

 *   is cleared in the TLB miss handler before the TLB entry is loaded.

 * - All other bits of the PTE are loaded into TLBLO without

 *   modification, leaving us only the bits 20, 21, 24, 25, 26, 30 for

 *   software PTE bits.  We actually use use bits 21, 24, 25, and

 *   software PTE bits.  We actually use bits 21, 24, 25, and

 *   30 respectively for the software bits: ACCESSED, DIRTY, RW, and

 *   PRESENT.

 */