Don't call gdbarch_pseudo_register_read_value in jit.c

Don't call gdbarch_pseudo_register_read_value in jit.c

gdbarch_pseudo_register_read_value is not implemented in every gdbarch, so
the predicate gdbarch_pseudo_register_read_value_p is needed before
calling it.  However, there is no such guard in jit_frame_prev_register, I
am wondering how does jit work on the arch without having gdbarch method
pseudo_register_read_value.

The proper way to get register value is to call cooked_read, and then
create the value object from the buffer.

gdb:

2018-01-22  Yao Qi  <yao.qi@linaro.org>

	* jit.c (jit_frame_prev_register): Call regcache::cooked_read
	instead of gdbarch_pseudo_register_read_value.