AArch64: Add inlining support for ceil(), floor(), rint(), round()

This patch adds inlining support for the following Math, StrictMath
methods in the ARM64 backend:
  * double ceil(double)
  * double floor(double)
  * double rint(double)
  * long round(double)
  * int round(float)

Also some cleanup.

Change-Id: I9f5a2f4065b1313649f4b0c4380b8176703c3fe1
Signed-off-by: Serban Constantinescu <serban.constantinescu@arm.com>