i386: Modernize AMD processor types

i386: Modernize AMD processor types

Use iterative PTA definitions for members of the same AMD processor family.

Also, fix a couple of related M_CPU_TYPE/M_CPU_SUBTYPE inconsistencies.

No functional changes intended.

gcc/ChangeLog:

	* config/i386/i386.h: Add PTA_BDVER1, PTA_BDVER2, PTA_BDVER3,
	PTA_BDVER4, PTA_BTVER1 and PTA_BTVER2.
	* common/config/i386/i386-common.cc (processor_alias_table)
	<"bdver1">: Use PTA_BDVER1.
	<"bdver2">: Use PTA_BDVER2.
	<"bdver3">: Use PTA_BDVER3.
	<"bdver4">: Use PTA_BDVER4.
	<"btver1">: Use PTA_BTVER1.  Use M_CPU_TYPE (AMD_BTVER1).
	<"btver2">: Use PTA_BTVER2.
	<"shanghai>: Use M_CPU_SUBTYPE (AMDFAM10H_SHANGHAI).
	<"istanbul>: Use M_CPU_SUBTYPE (AMDFAM10H_ISTANBUL).