Replace regcache_raw_read with regcache->raw_read

Replace regcache_raw_read with regcache->raw_read

The patch later in this series will move regcache's raw_read and
cooked_read methods to a new class regcache_read, and regcache is
dervied from it.  Also pass regcache_read instead of regcache to gdbarch
methods pseudo_register_read and pseudo_register_read_value.  In order
to prepare for this change, this patch changes regcache_raw_read to
regcache->raw_read.  On the other hand, since we are in C++, I prefer
using class method (regcache->raw_read).

gdb:

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

	* aarch64-tdep.c (aarch64_pseudo_read_value): Call regcache
	method raw_read instead of regcache_raw_read.
	* amd64-tdep.c (amd64_pseudo_register_read_value): Likewise.
	* arm-tdep.c (arm_neon_quad_read): Likewise.
	* avr-tdep.c (avr_pseudo_register_read): Likewise.
	* bfin-tdep.c (bfin_pseudo_register_read): Likewise.
	* frv-tdep.c (frv_pseudo_register_read): Likewise.
	* h8300-tdep.c (h8300_pseudo_register_read): Likewise.
	* i386-tdep.c (i386_mmx_regnum_to_fp_regnum): Likewise.
	(i386_pseudo_register_read_into_value): Likewise.
	* mep-tdep.c (mep_pseudo_cr32_read): Likewise.
	* msp430-tdep.c (msp430_pseudo_register_read): Likewise.
	* nds32-tdep.c (nds32_pseudo_register_read): Likewise.
	* rl78-tdep.c (rl78_pseudo_register_read): Likewise.
	* s390-linux-tdep.c (s390_pseudo_register_read): Likewise.
	* sparc-tdep.c (sparc32_pseudo_register_read):  Likewise.
	* sparc64-tdep.c (sparc64_pseudo_register_read): Likewise.
	* spu-tdep.c (spu_pseudo_register_read_spu):  Likewise.
	* xtensa-tdep.c (xtensa_pseudo_register_read): Likewise.