xen/arm: fix affected memory range by dcache clean functions

xen/arm: fix affected memory range by dcache clean functions

clean_dcache_va_range and clean_and_invalidate_dcache_va_range don't
calculate the range correctly when "end" is not cacheline aligned. As a
result, the last cacheline is not skipped. Fix the issue by aligning the
start address to the cacheline size.

In addition, make the code simpler and faster in
invalidate_dcache_va_range, by removing the module operation and using
bitmasks instead. Also remove the size adjustments in
invalidate_dcache_va_range, because the size variable is not used later
on.

Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Reviewed-by: Julien Grall <julien.grall@arm.com>
Tested-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>