gdbstub: update aarch64-core.xml

gdbstub: update aarch64-core.xml

Update aarch64-core.xml to include field definitions for PSTATE, which
in gdb is modelled in the cpsr (current program status register)
pseudo-register, named after the actual cpsr register in armv7.

Defining the fields layout of the register allows easy inspection of for
example, the current exception level (EL):

For example. Before booting a Linux guest, EL=2, but after booting and
Ctrl-C'ing in gdb, we get EL=0:

  (gdb) info registers $cpsr
  cpsr           0x20402009          [ SP EL=2 BTYPE=0 PAN C ]
  (gdb) cont
  Continuing.
  ^C
  Thread 2 received signal SIGINT, Interrupt.
  0x0000ffffaaff286c in ?? ()
  (gdb) info registers $cpsr
  cpsr           0x20001000          [ EL=0 BTYPE=0 SSBS C ]

The aarch64-core.xml has been updated to match exactly the version
retrieved from upstream gdb, retrieved in 2025-05-19 from HEAD commit
9f4dc0b137c86f6ff2098cb1ab69442c69d6023d.

Link: https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=gdb/features/aarch64-core.xml;h=b8046510b9a085d30463d37b3ecc8d435f5fb7a4;hb=HEAD
Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Message-Id: <20250519-gdbstub-aarch64-pstate-xml-v1-1-b4dbe87fe7c6@linaro.org>
[AJB: expanded upstream link]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-ID: <20250603110204.838117-18-alex.bennee@linaro.org>