cma: do some clean up

1. use "PFN_DOWN(r->size)" instead of "r->size >> PAGE_SHIFT".
2. adjust the function structure, one for the success path, the other for the failure path.

Xishi Qiu (2):
cma: use macro PFN_DOWN when converting size to pages
cma: adjust goto branch in function cma_create_area()

 drivers/base/dma-contiguous.c |   21 +++++++++++----------
 1 files changed, 11 insertions(+), 10 deletions(-)