readme: bump supported boards count

README.md

@@ -50,7 +50,7 @@ but not limited to:
 * a preemptive, tickless scheduler with priorities
 * flexible memory management
 * high resolution, long-term timers
-* support for AVR, MSP430, MIPS, ARM7, and ARM Cortex-M on over 80 boards
+* support 100+ boards based on AVR, MSP430, MIPS, ARM7 and ARM Cortex-M
 * the native port allows to run RIOT as-is on Linux, BSD, and MacOS. Multiple
   instances of RIOT running on a single machine can also be interconnected via
   a simple virtual Ethernet bridge