#88 riscv64: fix efibind.h missing/duplicate types

[Pete Batard]

The RISC-V 64 definition for CHAR8 is missing, so add it.
Likewise, BOOLEAN is defined in inc/efidef.h, so remove it.

Without these changes, gcc may produce compilation errors such as:
- error: unknown type name ‘CHAR8’
- error: conflicting types for ‘BOOLEAN’

[Nigel Croxon]

commit 1de509497826faa0ad84b82f5e2c3d21ee613459
Author: Moody Liu mooodyhunter@outlook.com
Date: Sat May 13 17:39:16 2023 +0100

riscv64: adjust type definitions

CHAR8 needs to be defined while BOOLEAN should be removed
here to prevent typedef conflicts

Signed-off-by: Moody Liu <mooodyhunter@outlook.com>