RISC-V: load initrd wherever it fits into memory

Requiring that initrd is loaded below RAM start + 256 MiB led to failure
to boot SUSE Linux with GRUB on QEMU, cf.
https://lists.gnu.org/archive/html/grub-devel/2021-06/msg00037.html

Remove the constraint.

Reported-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Fixes: d707174 ("RISC-V: Add EFI stub support.")
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/include/asm/efi.h

@@ -27,10 +27,10 @@ int efi_set_mapping_permissions(struct mm_struct *mm, efi_memory_desc_t *md);
 
 #define ARCH_EFI_IRQ_FLAGS_MASK (SR_IE | SR_SPIE)
 
-/* Load initrd at enough distance from DRAM start */
+/* Load initrd anywhere in system RAM */
 static inline unsigned long efi_get_max_initrd_addr(unsigned long image_addr)
 {
-	return image_addr + SZ_256M;
+	return ULONG_MAX;
 }
 
 #define alloc_screen_info(x...)		(&screen_info)