Check always_inline flag in s390_can_inline_p [PR104327]

Check always_inline flag in s390_can_inline_p [PR104327]

MASK_MVCLE is set for -Os but not for other optimization levels. In
general it should not make much sense to inline across calls where the
flag is different but we have to allow it for always_inline.

The patch also rearranges the hook implementation a bit based on the
recommendations from Jakub und Martin in the PR.

Bootstrapped and regression tested on s390x with various arch flags.
Will commit after giving a few days for comments.

gcc/ChangeLog:

	PR target/104327
	* config/s390/s390.cc (s390_can_inline_p): Accept a few more flags
	if always_inline is set. Don't inline when tune differs without
	always_inline.

gcc/testsuite/ChangeLog:

	PR target/104327
	* gcc.c-torture/compile/pr104327.c: New test.