arm: mm: fix and cleanup function to print vmalloc info

print_vmalloc_lowmem_info incorrectly uses __va macro for
highmem addresses to print vmalloc and lowmem region
information. This results in incorrect prints particularly
for platforms with higher DDR sizes where the __va wraps
and gives incorrect virtual addresses. Fix this and
simplify whole function.

Change-Id: I375fbba502b677da31115f54772e6d646f27792a
Signed-off-by: Shiraz Hashim <shashim@codeaurora.org>