Rollup merge of #136194 - taiki-e:bpf-clobber-abi, r=amanieu

Support clobber_abi in BPF inline assembly

This supports [`clobber_abi`](https://doc.rust-lang.org/nightly/reference/inline-assembly.html#abi-clobbers) which is one of the requirements of stabilization mentioned in the tracking Issue for `asm_experimental_arch` (#93335).

Refs: [Section 1.1 "Registers and calling convention" in BPF ABI Recommended Conventions and Guidelines v1.0](https://github.com/torvalds/linux/blob/v6.13/Documentation/bpf/standardization/abi.rst#11registers-and-calling-convention)
> R0 - R5 are scratch registers and BPF programs needs to spill/fill them if necessary across calls.

cc `@alessandrod` `@dave-tucker` `@tamird` `@vadorovsky` (target maintainers mentioned in platform support document which will be added by rust-lang/rust#135107)

r? `@Amanieu`

`@rustbot` label +O-eBPF +A-inline-assembly

Author: matthiaskrgr