powerpc: E6500: Move macro CONFIG_E6500 to Kconfig

Use Kconfig option E6500 and clean up existing usage.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/arch/powerpc/cpu/mpc85xx/Kconfig b/arch/powerpc/cpu/mpc85xx/Kconfig
index 0524172..d151f49 100644
--- a/arch/powerpc/cpu/mpc85xx/Kconfig
+++ b/arch/powerpc/cpu/mpc85xx/Kconfig
@@ -330,6 +330,7 @@
 config ARCH_B4420
 	bool
 	select E500MC
+	select E6500
 	select FSL_LAW
 	select SYS_FSL_DDR_VER_47
 	select SYS_FSL_ERRATUM_A004477
@@ -350,6 +351,7 @@
 config ARCH_B4860
 	bool
 	select E500MC
+	select E6500
 	select FSL_LAW
 	select SYS_FSL_DDR_VER_47
 	select SYS_FSL_ERRATUM_A004477
@@ -806,6 +808,7 @@
 config ARCH_T2080
 	bool
 	select E500MC
+	select E6500
 	select FSL_LAW
 	select SYS_FSL_DDR_VER_47
 	select SYS_FSL_ERRATUM_A006379
@@ -822,6 +825,7 @@
 config ARCH_T2081
 	bool
 	select E500MC
+	select E6500
 	select FSL_LAW
 	select SYS_FSL_DDR_VER_47
 	select SYS_FSL_ERRATUM_A006379
@@ -838,6 +842,7 @@
 config ARCH_T4160
 	bool
 	select E500MC
+	select E6500
 	select FSL_LAW
 	select SYS_FSL_DDR_VER_47
 	select SYS_FSL_ERRATUM_A004468
@@ -855,6 +860,7 @@
 config ARCH_T4240
 	bool
 	select E500MC
+	select E6500
 	select FSL_LAW
 	select SYS_FSL_DDR_VER_47
 	select SYS_FSL_ERRATUM_A004468
@@ -885,6 +891,11 @@
 	help
 		Enble PowerPC E500MC core
 
+config E6500
+	bool
+	help
+		Enable PowerPC E6500 core
+
 config FSL_LAW
 	bool
 	help
@@ -1165,6 +1176,11 @@
 		Number of local access windows. This is fixed per SoC.
 		If not sure, do not change.
 
+config SYS_FSL_THREADS_PER_CORE
+	int
+	default 2 if E6500
+	default 1
+
 config SYS_NUM_TLBCAMS
 	int "Number of TLB CAM entries"
 	default 64 if E500MC