Merge branch 's390-bpf-describe-the-frame-using-a-struct-instead-of-constants'

Ilya Leoshkevich says:

====================
s390/bpf: Describe the frame using a struct instead of constants

Hi,

This series contains two small refactorings without functional changes.

The first one removes the code duplication around calculating the
distance from %r15 to the stack frame.

The second one simplifies how offsets to various values stored inside
the frame are calculated.

Best regards,
Ilya
====================

Link: https://patch.msgid.link/20250624121501.50536-1-iii@linux.ibm.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>