feat(core): allow for model R in firmware build

As model R will run on the same computational hardware as model T,
memory_R.ld is just a symbolic link to memory_T.ld.

[no changelog]

core/embed/firmware/header.S

@@ -26,13 +26,13 @@ g_header:
     . = . + 8                        // reserved
     . = . + 512                      // hash1 ... hash16
 
-#if defined TREZOR_MODEL_T
-// model T header specifics
+#if !defined TREZOR_MODEL_1
+// trezor-core header style
     . = . + 415                      // reserved
     .byte 0                          // sigmask
     . = . + 64                       // sig
-#elif defined TREZOR_MODEL_1
-// model 1 header specifics
+#else
+// model 1 compatibility header
     . = . + 64                       // sig1
     . = . + 64                       // sig2
     . = . + 64                       // sig3
@@ -41,8 +41,6 @@ g_header:
     .byte 0                          // sigindex3
     . = . + 220                      // reserved
     . = . + 65                       // reserved
-#else
-#error Unknown Trezor model
 #endif
 
 g_header_end:

core/embed/firmware/main.c

@@ -65,7 +65,7 @@ int main(void) {
 #endif
 
   // reinitialize HAL for Trezor One
-#if defined TREZOR_MODEL_1
+#if defined TREZOR_MODEL_1 || defined TREZOR_MODEL_R
   HAL_Init();
 #endif
 
@@ -86,7 +86,7 @@ int main(void) {
   // Init peripherals
   pendsv_init();
 
-#if defined TREZOR_MODEL_1
+#if defined TREZOR_MODEL_1 || defined TREZOR_MODEL_R
   display_init();
   button_init();
 #endif

core/embed/firmware/memory_R.ld

@@ -0,0 +1 @@
+memory_T.ld

core/embed/firmware/startup.S

@@ -48,7 +48,7 @@ reset_handler:
   // according to "ARM Cortex-M Programming Guide to Memory Barrier Instructions" Application Note 321, section 4.7:
   // "If it is not necessary to ensure that a pended interrupt is recognized immediately before
   // subsequent operations, it is not necessary to insert a memory barrier instruction."
-#if defined TREZOR_MODEL_T
+#if defined TREZOR_MODEL_T || defined TREZOR_MODEL_R
   cpsie f
 #elif defined TREZOR_MODEL_1
   cpsie if