File gdb-fix-riscv-tdep.patch of Package gdb

In gdb-rhbz795424-bitpos-20of25.patch, the TYPE_LENGTH is changed from
unsigned to ULONGEST.

This breaks the build on RISC-V:
...
gdb/riscv-tdep.c: In function 'int riscv_type_alignment(type*)':
gdb/riscv-tdep.c:1648:64: error: no matching function for call to \
  'min(ULONGEST&, unsigned int)'
   return std::min (TYPE_LENGTH (t), (unsigned) BIGGEST_ALIGNMENT);
...

Fix this by backporting a fragment of an unrelated commit on master that
also changes TYPE_LENGTH from unsigned to ULONGEST.
...
$ git show --pretty=%p cc1defb1dc gdb/riscv-tdep.c
...

diff --git a/gdb/riscv-tdep.c b/gdb/riscv-tdep.c
index 8a996f32d3..ff5f36e762 100644
--- a/gdb/riscv-tdep.c
+++ b/gdb/riscv-tdep.c
@@ -1645,7 +1645,7 @@ riscv_type_alignment (struct type *t)
 
     case TYPE_CODE_ARRAY:
       if (TYPE_VECTOR (t))
-	return std::min (TYPE_LENGTH (t), (unsigned) BIGGEST_ALIGNMENT);
+	return std::min (TYPE_LENGTH (t), (ULONGEST) BIGGEST_ALIGNMENT);
       /* FALLTHROUGH */
 
     case TYPE_CODE_COMPLEX: