lib: sbi/sbi_domain: cosmetic style fixes

Minor updates to the comments for language and style fixes.

Signed-off-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Anup Patel <anup@brainfault.org>

lib/sbi/sbi_domain.c

@@ -337,7 +337,7 @@ static int sanitize_domain(const struct sbi_platform *plat,
 	/*
 	 * Check next mode
 	 *
-	 * We only allow next mode to be S-mode or U-mode.so that we can
+	 * We only allow next mode to be S-mode or U-mode, so that we can
 	 * protect M-mode context and enforce checks on memory accesses.
 	 */
 	if (dom->next_mode != PRV_S &&