Fixed GCC ARM linker script for STM32L1  (STM32L152XE.ld)

Fixed Flash and RAM definitions in GCC ARM linker script for STM32L1
(STM32L152XE.ld)
Updated linker script to reserve space for BootRAM

Updated linker script to reserve space for BootRAM at 0x138
Change comment to GCC scripts

Change comment to GCC scripts. All GCC linker scrips for STM32L1 have
space for BootRAM defined.
Merge pull request #748 from modtronix-com/master

Targets: Fix GCC ARM linker script for STM32L1  (STM32L152XE)