linux-user: Emulate /proc/cpuinfo on s390x

linux-user: Emulate /proc/cpuinfo on s390x

Some s390x userspace programs are confused when seeing a foreign
/proc/cpuinfo [1]. Add the emulation for s390x; follow the respective
kernel code structure where possible.

Output example:

	vendor_id       : IBM/S390
	# processors    : 12
	bogomips per cpu: 13370.00
	max thread id   : 0
	features	: esan3 zarch stfle msa
	facilities      : 0 1 2 3 4 7 9 16 17 18 19 21 22 24 25 27 30 31 32 33 34 35 37 40 41 45 49 51 52 53 57 58 61 69 71 72 75 76 77 129 130 131 135 138 146 148
	processor 0: version = 00,  identification = 000000,  machine = 8561
	processor 1: version = 00,  identification = 100000,  machine = 8561
	[...]

	cpu number      : 0
	version         : 00
	identification  : 000000
	machine         : 8561

	cpu number      : 1
	version         : 00
	identification  : 100000
	machine         : 8561
	[...]

[1] https://bugzilla.redhat.com/show_bug.cgi?id=2211472

Reported-by: Tulio Magno Quites Machado Filho <tuliom@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Message-Id: <20230605113950.1169228-5-iii@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>