stm32lx: refactor and add support for STM32L0xx

stm32lx: refactor and add support for STM32L0xx

This adds initial support for the STM32L0 family, specifically the ID
code 417 variant.  The 'L0 has 128B rather than 256B pages as well as a
different number of pages per sector.  It also has several key registers
and register sets in different locations from the STM32L1xx parts.

This change therefore takes the opportunity to reorganize part information into
a const table (it was previously determined by a set of control statements) and
abstracts away some of the low-level details to make them generic for L1 and
L0 parts.

We also include the first bank's size (for dual bank parts) in the new
device information table (and correct that size for the 0x437 variant
which is 256 rather than 192KB).

The 'L0 parts will not use the built-in loader/helper for Flash writing.

Tested on STM32L053 (dicovery board and Nucleo board) and STM32L152
(discovery board).

Change-Id: I57f7a8ab02caee266de71b31ae82a50d85728a0b
Signed-off-by: Andrey Yurovsky <yurovsky@gmail.com>
Reviewed-on: http://openocd.zylin.com/2200
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>