linux-user: Emulate /proc/cpuinfo on aarch64 and arm

Add emulation for /proc/cpuinfo for arm architecture.
The output below mimics output as seen on debian porterboxes.

aarch64 output example:

processor       : 0
model name      : ARMv8 Processor rev 0 (v8l)
BogoMIPS        : 100.00
Features        : swp half thumb fast_mult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae aes pmull sha1 sha2 crc32
CPU implementer : 0x41
CPU architecture: 8
CPU variant     : 0x1
CPU part        : 0xd07
CPU revision    : 0

arm 32-bit output example:

processor	: 0
model name	: ARMv7 Processor rev 5 (armv7l)
BogoMIPS	: 100.00
Features	: swp half thumb fast_mult vfp edsp thumbee neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae
CPU implementer	: 0x41
CPU architecture: 7
CPU variant	: 0x0f
CPU part	: 0xc07
CPU revision	: 5

Signed-off-by: Helge Deller <deller@gmx.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230803214450.647040-3-deller@gmx.de>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>