arm64: kernel: Add arch specific bug.h

Arch specific bug.h is required to get the complete register
dump on a BUG invocation. For this feature to work completely
including the information for file and line, we need to add
CONFIG_GENERIC_BUG to arm64 and provide the dependent APIs.

Change-Id: I0f894bcb182fd3a5d32c7e11391a4977e59d18ec
Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>