powerpc/mm: Move tlbcam_sz() and make it static

Building with W=1 we see a warning:
  linux/arch/powerpc/mm/nohash/fsl_book3e.c:63:15: error: no previous prototype for ‘tlbcam_sz’

tlbcam_sz() is not used outside this file, so we can make it static.
However it's only used inside #ifdef CONFIG_PPC32, so move it within
that ifdef, otherwise we would get a defined but not used error.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211124093254.1054750-4-mpe@ellerman.id.au

arch/powerpc/mm/nohash/fsl_book3e.c

@@ -60,11 +60,6 @@ struct tlbcamrange {
 	phys_addr_t phys;
 } tlbcam_addrs[NUM_TLBCAMS];
 
-unsigned long tlbcam_sz(int idx)
-{
-	return tlbcam_addrs[idx].limit - tlbcam_addrs[idx].start + 1;
-}
-
 #ifdef CONFIG_FSL_BOOKE
 /*
  * Return PA for this VA if it is mapped by a CAM, or 0
@@ -264,6 +259,11 @@ void __init MMU_init_hw(void)
 	flush_instruction_cache();
 }
 
+static unsigned long tlbcam_sz(int idx)
+{
+	return tlbcam_addrs[idx].limit - tlbcam_addrs[idx].start + 1;
+}
+
 void __init adjust_total_lowmem(void)
 {
 	unsigned long ram;