riscv/head: fix misspelling of guaranteed

Fixes misspelling of guaranteed in comment describing why fetching fence
is guaranteed to work when switching to kernel page tables.
Signed-off-by: hasheddan <georgedanielmangum@gmail.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/kernel/head.S

@@ -135,7 +135,7 @@ relocate:
 	/*
 	 * Switch to kernel page tables.  A full fence is necessary in order to
 	 * avoid using the trampoline translations, which are only correct for
-	 * the first superpage.  Fetching the fence is guarnteed to work
+	 * the first superpage.  Fetching the fence is guaranteed to work
 	 * because that first superpage is translated the same way.
 	 */
 	csrw CSR_SATP, a2