x86/ioperm: Use atomic64_inc_return() in ksys_ioperm()

Use atomic64_inc_return(&ref) instead of atomic64_add_return(1, &ref)
to use optimized implementation on targets that define
atomic_inc_return() and to remove now unneeded initialization of the
%eax/%edx register pair before the call to atomic64_inc_return().

On x86_32 the code improves from:

 1b0:    b9 00 00 00 00           mov    $0x0,%ecx
            1b1: R_386_32    .bss
 1b5:    89 43 0c                 mov    %eax,0xc(%ebx)
 1b8:    31 d2                    xor    %edx,%edx
 1ba:    b8 01 00 00 00           mov    $0x1,%eax
 1bf:    e8 fc ff ff ff           call   1c0 <ksys_ioperm+0xa8>
            1c0: R_386_PC32    atomic64_add_return_cx8
 1c4:    89 03                    mov    %eax,(%ebx)
 1c6:    89 53 04                 mov    %edx,0x4(%ebx)

to:

 1b0:    be 00 00 00 00           mov    $0x0,%esi
            1b1: R_386_32    .bss
 1b5:    89 43 0c                 mov    %eax,0xc(%ebx)
 1b8:    e8 fc ff ff ff           call   1b9 <ksys_ioperm+0xa1>
            1b9: R_386_PC32    atomic64_inc_return_cx8
 1bd:    89 03                    mov    %eax,(%ebx)
 1bf:    89 53 04                 mov    %edx,0x4(%ebx)

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20250223161355.3607-1-ubizjak@gmail.com