powerpc: Use pr_devel() in do_dcache_icache_coherency()

pr_debug() can now result in code being generated even when DEBUG
is not defined. That's not really desirable in some places.

With CONFIG_DYNAMIC_DEBUG=y:

size before:
   text    data     bss     dec     hex filename
   2036     368       8    2412     96c arch/powerpc/mm/pgtable.o

size after:
   text    data     bss     dec     hex filename
   1677     248       8    1933     78d arch/powerpc/mm/pgtable.o

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/mm/pgtable.c

@@ -129,12 +129,12 @@ static pte_t do_dcache_icache_coherency(pte_t pte)
 	page = pfn_to_page(pfn);
 
 	if (!PageReserved(page) && !test_bit(PG_arch_1, &page->flags)) {
-		pr_debug("do_dcache_icache_coherency... flushing\n");
+		pr_devel("do_dcache_icache_coherency... flushing\n");
 		flush_dcache_icache_page(page);
 		set_bit(PG_arch_1, &page->flags);
 	}
 	else
-		pr_debug("do_dcache_icache_coherency... already clean\n");
+		pr_devel("do_dcache_icache_coherency... already clean\n");
 	return __pte(pte_val(pte) | _PAGE_HWEXEC);
 }