MIPS: Loongson: Add UEFI-like firmware interface (LEFI) support

MIPS: Loongson: Add UEFI-like firmware interface (LEFI) support

The new UEFI-like firmware interface (LEFI, i.e. Loongson Unified
Firmware Interface) has 3 advantages:

1, Firmware export a physical memory map which is similar to X86's
   E820 map, so prom_init_memory() will be more elegant that #ifdef
   clauses can be removed.
2, Firmware export a pci irq routing table, we no longer need pci
   irq routing fixup in kernel's code.
3, Firmware has a built-in vga bios, and its address is exported,
   the linux kernel no longer need an embedded blob.

With the LEFI interface, Loongson-3A/2G and all their successors can use
a unified kernel. All Loongson-based machines support this new interface
except 2E/2F series.

Signed-off-by: Huacai Chen <[email protected]>
Signed-off-by: Hongliang Tao <[email protected]>
Signed-off-by: Hua Yan <[email protected]>
Tested-by: Alex Smith <[email protected]>
Reviewed-by: Alex Smith <[email protected]>
Cc: John Crispin <[email protected]>
Cc: Steven J. Hill <[email protected]>
Cc: Aurelien Jarno <[email protected]>
Cc: [email protected]
Cc: Fuxin Zhang <[email protected]>
Cc: Zhangjin Wu <[email protected]>
Patchwork: https://patchwork.linux-mips.org/patch/6632
Signed-off-by: Ralf Baechle <[email protected]>