sparc: Make sure we mmap at SHMLBA alignment

SPARC Linux has an oddity that it insists that mmap()
of MAP_FIXED memory must be at an alignment defined by
SHMLBA, which is more aligned than the page size
(typically, SHMLBA alignment is to 16K, and pages are 8K).
This is a relic of ancient hardware that had cache
aliasing constraints, but even on modern hardware the
kernel still insists on the alignment.

To ensure that we get mmap() alignment sufficient to
make the kernel happy, change QEMU_VMALLOC_ALIGN,
qemu_fd_getpagesize() and qemu_mempath_getpagesize()
to use the maximum of getpagesize() and SHMLBA.

In particular, this allows 'make check' to pass on Sparc:
we were previously failing the ivshmem tests.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 1512752248-17857-1-git-send-email-peter.maydell@linaro.org
