msm: smem: clarify SBL misconfiguration error messages

SMEM must be initialized by the secondary bootloader (SBL) before Linux
is booted and the SMEM driver is initialized.  If it is not initialized,
error messages are printed and SMEM is disabled.  Some of these error
messages can be misinterpreted to be a Linux configuration issue instead
of an SBL issue which delays resolving the misconfiguration.

Add additional code comments and change the error messages to make it
clear that the SBL has not initialized SMEM.

Change-Id: I1d80245337fbfb708a070d56c65c293aed9a2b6b
Signed-off-by: Eric Holmberg <eholmber@codeaurora.org>