Documentation: riscv: Update boot image header since EFI stub is supported

The EFI stub is supported on RISC-V so update the documentation that
explains how the boot image header was reused to support it.

Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20230817130734.10387-3-alexghiti@rivosinc.com

Author: Alexandre Ghiti

Documentation/riscv/boot-image-header.rst

@@ -28,11 +28,11 @@ header in future.
 Notes
 =====
 
-- This header can also be reused to support EFI stub for RISC-V in future. EFI
-  specification needs PE/COFF image header in the beginning of the kernel image
-  in order to load it as an EFI application. In order to support EFI stub,
-  code0 should be replaced with "MZ" magic string and res3(at offset 0x3c) should
-  point to the rest of the PE/COFF header.
+- This header is also reused to support EFI stub for RISC-V. EFI specification
+  needs PE/COFF image header in the beginning of the kernel image in order to
+  load it as an EFI application. In order to support EFI stub, code0 is replaced
+  with "MZ" magic string and res3(at offset 0x3c) points to the rest of the
+  PE/COFF header.
 
 - version field indicate header version number