RISC-V: Define MAXPHYSMEM_1GB only for RV32

MAXPHYSMEM_1GB option was added for RV32 because RV32 only supports 1GB
of maximum physical memory. This lead to few compilation errors reported
by kernel test robot which created the following configuration combination
which are not useful but can be configured.

1. MAXPHYSMEM_1GB & RV64
2, MAXPHYSMEM_2GB & RV32

Fix this by restricting MAXPHYSMEM_1GB for RV32 and MAXPHYSMEM_2GB only for
RV64.

Fixes: e5577937 ("RISC-V: Fix maximum allowed phsyical memory for RV32")
Cc: stable@vger.kernel.org
Reported-by: NRandy Dunlap <rdunlap@infradead.org>
Acked-by: NRandy Dunlap <rdunlap@infradead.org>
Tested-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NAtish Patra <atish.patra@wdc.com>
Signed-off-by: NPalmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/Kconfig

@@ -252,8 +252,10 @@ choice
 	default MAXPHYSMEM_128GB if 64BIT && CMODEL_MEDANY
 
 	config MAXPHYSMEM_1GB
+		depends on 32BIT
 		bool "1GiB"
 	config MAXPHYSMEM_2GB
+		depends on 64BIT && CMODEL_MEDLOW
 		bool "2GiB"
 	config MAXPHYSMEM_128GB
 		depends on 64BIT && CMODEL_MEDANY