drm/amdkfd: avoid CONFIG_ prefix for non-Kconfig symbols

The CONFIG_ prefix is reserved for Kconfig options in Make and CPP
syntax.  Various static analysis tools rely on this naming convention
and check if CONFIG_ prefixed symbols are defined Kconfig.  Hence add
yet another prefix AMD_ to CONFIG_REG_{BASE,END,SISE} to apply to this
convention and make static analysis tools happy.

Signed-off-by: Valentin Rothberg <valentinrothberg@gmail.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>