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