drivers: soc: qcom: Make global minidump table pointer NULL

If SMEM has not been initialized yet, before returning EPROBE_DEFER, make
the global minidump table pointer NULL. This avoids the kernel page fault
while trying to dereference the pointer later.

Change-Id: I76cbbee82e5b9fa02e0caaac57db2d6ce8f6ea6e
Signed-off-by: Prakruthi Deepak Heragu <pheragu@codeaurora.org>