exec: Move CPUTLBEntry helpers to cputlb.c

exec: Move CPUTLBEntry helpers to cputlb.c

The following CPUTLBEntry helpers are only used in accel/tcg/cputlb.c:
  - tlb_index()
  - tlb_entry()
  - tlb_read_idx()
  - tlb_addr_write()

Move them to this file, allowing to remove the huge "cpu.h" header
inclusion from "exec/cpu_ldst.h".

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20240418192525.97451-13-philmd@linaro.org>