msm: pm-boot: clean up non TZ support code

Modern ARM processors supporting TZ environment by
default. Currently, cores warmboot starts from TZ when
there is a TZ support. This patch removes the non TZ
supported code.

Change-Id: Ifa5df40bd649e4860a2660132f3fc30fa7937358
Signed-off-by: Murali Nalajala <mnalajal@codeaurora.org>