RISC-V: Use tabs to align macro values in asm/csr.h

The spacing between macro name and value is not consistent in
asm/csr.h. This patch beautifies asm/csr.h by using tabs to align
macro values instead of spaces.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>