Ram size corrected.

It was wrongly set to 61KB.
It is actually 48KB for RC, and 64 for RD and RE, but I am using 64KB in
an RCT6 mcu without any issue.

Author: victorpv

STM32F1/variants/generic_stm32f103r/ld/stm32f103re-bootloader.ld

@@ -21,7 +21,7 @@
  */
 MEMORY
 {
-ram (rwx) : ORIGIN = 0x20000000, LENGTH = 61K
+ram (rwx) : ORIGIN = 0x20000000, LENGTH = 64K
 rom (rx) : ORIGIN = 0x08002000, LENGTH = 504K
 }