perf tools: Add get_unaligned_leNN()

Add get_unaligned_le16(), get_unaligned_le32 and get_unaligned_le64, same
as include/asm-generic/unaligned.h. And add include/asm-generic/unaligned.h
to check-headers.sh bringing tools/include/asm-generic/unaligned.h up to
date so that the kernel and tools versions match.

Use diagnostic pragmas to ignore -Wpacked used by perf build.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20231005190451.175568-2-adrian.hunter@intel.com
Link: https://lore.kernel.org/r/20231010142234.20061-1-adrian.hunter@intel.com


[ squashed check-header.sh addition ]
Signed-off-by: Namhyung Kim <namhyung@kernel.org>