esp32: allow up to 8 kB of ULP program size

The remaining 4 kB had been reserved for storing RF calibration and
BT stack state since 4e092be6. However, these features never got
implemented. If we ever need to place RF related data into RTC slow
memory, we can do this by creating a variable with RTC_NOINIT_ATTR
instead.

Closes https://github.com/espressif/esp-idf/issues/3993

components/esp32/ld/esp32.ld

@@ -95,7 +95,7 @@ MEMORY
      Start of RTC slow memory is reserved for ULP co-processor code + data, if enabled.
   */
   rtc_slow_seg(RW)  :                org = 0x50000000 + CONFIG_ESP32_ULP_COPROC_RESERVE_MEM,
-                                     len = 0x1000 - CONFIG_ESP32_ULP_COPROC_RESERVE_MEM
+                                     len = 0x2000 - CONFIG_ESP32_ULP_COPROC_RESERVE_MEM
 
   /* external memory ,including data and text */
   extern_ram_seg(RWX)  :             org = 0x3F800000,

components/esp_rom/include/esp32/rom/rtc.h

@@ -45,8 +45,7 @@ extern "C" {
   *************************************************************************************
   *     rtc memory addr         type    size            usage
   *     0x3ff61000(0x50000000)  Slow    SIZE_CP         Co-Processor code/Reset Entry
-  *     0x3ff61000+SIZE_CP      Slow    4096-SIZE_CP
-  *     0x3ff62800              Slow    4096            Reserved
+  *     0x3ff61000+SIZE_CP      Slow    8192-SIZE_CP
   *
   *     0x3ff80000(0x400c0000)  Fast    8192            deep sleep entry code
   *