xtensa: Simplify the definition of REGNO_OK_FOR_BASE_P() and avoid calling it directly

xtensa: Simplify the definition of REGNO_OK_FOR_BASE_P() and avoid calling it directly

In recent gcc versions, REGNO_OK_FOR_BASE_P() is not called directly, but
rather via regno_ok_for_base_p() which is a wrapper in gcc/addresses.h.
The wrapper obtains a hard register number from pseudo via reg_renumber
array, so REGNO_OK_FOR_BASE_P() does not need to take this into
consideration.

On the other hand, since there is only one use of REGNO_OK_FOR_BASE_P()
in the target-specific code, it would make more sense to simplify the
definition of REGNO_OK_FOR_BASE_P() and replace its call with that of
regno_ok_for_base_p().

gcc/ChangeLog:

	* config/xtensa/xtensa.cc (#include):
	Add "addresses.h".
	* config/xtensa/xtensa.h (REGNO_OK_FOR_BASE_P):
	Simplify to just a call to GP_REG_P().
	(BASE_REG_P): Replace REGNO_OK_FOR_BASE_P() with the equivalent
	call to regno_ok_for_base_p().