gdbarch: Use an anonymous union for target data in `gdbarch_info'

gdbarch: Use an anonymous union for target data in `gdbarch_info'

As an update to commit ede5f15146ae ("gdbarch.h: Change
gdbarch_info::tdep_info's type to void *") replace the definition of the
`tdep_info' member in `struct gdbarch_info' with an anonymous union,
comprising the original member, with its type reverted to `struct
gdbarch_tdep_info *', a `tdesc_data' member of a `struct tdesc_arch_data
*' type and an `id' member of an `int *' type.  Remove now unnecessary
casts throughout use places then, making code easier to read an less
prone to errors, which may happen with casting.

	gdb/
	* gdbarch.sh (gdbarch_info): Replace the `tdep_info' member with
	a union of `tdep_info', `tdesc_data' and `id'.
	* aarch64-tdep.c (aarch64_gdbarch_init): Use `info.tdesc_data'
	rather than `info.tdep_info'.
	* amd64-linux-tdep.c (amd64_linux_init_abi): Likewise.
	* i386-linux-tdep.c (i386_linux_init_abi): Likewise.
	* i386-tdep.c (i386_gdbarch_init): Likewise.
	* mips-linux-tdep.c (mips_linux_init_abi): Likewise.
	* mips-tdep.c (mips_gdbarch_init): Likewise.
	* nds32-tdep.c (nds32_gdbarch_init): Likewise.
	* rs6000-tdep.c (rs6000_gdbarch_init): Likewise.
	* ppc-linux-tdep.c (ppu2spu_sniffer): Use `info.id' rather than
	`info.tdep_info'.
	(ppc_linux_init_abi): Use `info.tdesc_data' rather than
	`info.tdep_info'.
	* sparc-tdep.c (sparc32_gdbarch_init): Likewise.
	* spu-multiarch.c (spu_gdbarch): Use `info.id' rather than
	`info.tdep_info'.
	* spu-tdep.c (spu_gdbarch_init): Likewise.
	* gdbarch.h: Regenerate.