RISC-V: use RISCV_{INT,SHORT} instead of {INT,SHORT} for asm macros

INT and SHORT are used by some drivers that pull in the include files,
so prefixing helps avoid namespace conflicts. Other constructs in the
same file already uses this.

Fixes, among others, these warnings with allmodconfig:

../sound/core/pcm_misc.c:43:0: warning: "INT" redefined
 #define INT __force int

Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>