arm64/fixmap: make notes of fixed_addresses more precisely

These 'compile-time allocated' memory buffers can occupy more than one
page and each enum increment is page-sized. So improve the note about it.

Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/1596460720-19243-1-git-send-email-kernelfans@gmail.com
To: linux-arm-kernel@lists.infradead.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Author: liupingfan

arch/arm64/include/asm/fixmap.h

@@ -28,10 +28,9 @@
  * compile time, but to set the physical address only
  * in the boot process.
  *
- * These 'compile-time allocated' memory buffers are
- * page-sized. Use set_fixmap(idx,phys) to associate
- * physical memory with fixmap indices.
- *
+ * Each enum increment in these 'compile-time allocated'
+ * memory buffers is page-sized. Use set_fixmap(idx,phys)
+ * to associate physical memory with a fixmap index.
  */
 enum fixed_addresses {
 	FIX_HOLE,