xen/arm64: bitops: Match the register size with the value size in flsl

xen/arm64: bitops: Match the register size with the value size in flsl

Clang is pickier than GCC for the register size in asm statement. It expects
the register size to match the value size.

The instruction clz is expecting the two operands to be the same size
(i.e 32-bit or 64-bit). As the flsl function is dealing with 64-bit
value, we need to make the destination variable 64-bit as well.

While at it, add a newline before the return statement.

Note that the return type of flsl is not updated because the result will
always be smaller than 64 and therefore fit in 32-bit.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Release-acked-by: Juergen Gross <jgross@suse.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>