[nano 33 iot] move debug.svd_file inside boards.txt

this way it does not get defined in case the board does not support it

Author: umbynos

Diff for: boards.txt

@@ -257,7 +257,7 @@ nano_33_iot.build.pid=0x8057
 nano_33_iot.bootloader.tool=openocd
 nano_33_iot.bootloader.tool.default=openocd
 nano_33_iot.bootloader.file=nano_33_iot/samd21_sam_ba_arduino_nano_33_iot.bin
-nano_33_iot.build.svd_file={runtime.platform.path}/svd/at91samd21g18.svd
+nano_33_iot.debug.svd_file={runtime.platform.path}/svd/at91samd21g18.svd
 
 nano_33_iot.debug.cortex-debug.custom.postAttachCommands.0=set remote hardware-watchpoint-limit 2
 nano_33_iot.debug.cortex-debug.custom.postAttachCommands.1=monitor reset halt

Diff for: platform.txt

@@ -141,7 +141,6 @@ build.openocdinterface=interface/{programmer.protocol}.cfg
 debug.server.openocd.script={runtime.platform.path}/variants/{build.variant}/{build.openocdoldscript}
 debug.server.openocd.scripts.0={build.openocdinterface}
 debug.server.openocd.scripts.1={runtime.platform.path}/variants/{build.variant}/{build.openocdscript}
-debug.svd_file={build.svd_file}
 
 # Upload/Debug tools
 # ------------------