arch: remove the ARCH_PHYS_ADDR_T_64BIT config symbol

Instead select the PHYS_ADDR_T_64BIT for 32-bit architectures that need a
64-bit phys_addr_t type directly.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: James Hogan <jhogan@kernel.org>

arch/riscv/Kconfig

@@ -5,6 +5,8 @@
 
 config RISCV
 	def_bool y
+	# even on 32-bit, physical (and DMA) addresses are > 32-bits
+	select PHYS_ADDR_T_64BIT
 	select OF
 	select OF_EARLY_FLATTREE
 	select OF_IRQ
@@ -38,10 +40,6 @@ config RISCV
 config MMU
 	def_bool y
 
-# even on 32-bit, physical (and DMA) addresses are > 32-bits
-config ARCH_PHYS_ADDR_T_64BIT
-	def_bool y
-
 config ZONE_DMA32
 	bool
 	default y