x86/emul: Drop segment_attributes_t

x86/emul: Drop segment_attributes_t

The amount of namespace resolution is unnecessarily large, as all code deals
in terms of struct segment_register.  This removes the attr.fields part of all
references, and alters attr.bytes to just attr.

Three areas of code using initialisers for segment_register are tweaked to
compile with older versions of GCC.  arch_set_info_hvm_guest() has its SEG()
macros altered to use plain comma-based initialisation, while
{rm,vm86}_{cs,ds}_attr are simplified to plain numbers which matches their
description in the manuals.

No functional change.  (For some reason, the old {rm,vm86}_{cs,ds}_attr causes
GCC to create variable in .rodata, whereas the new code uses immediate
operands.  As a result, vmx_{get,set}_segment_register() are slightly
shorter.)

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>