boards: fix CONFIG_MM_REGIONS related warning in nightly build

fix the following warning:
chip/sam_allocateheap.c:120:8: warning: #warning "CONFIG_MM_REGIONS < 3: NFC SRAM not included in HEAP" [-Wcpp]
  120 | #      warning "CONFIG_MM_REGIONS < 3: NFC SRAM not included in HEAP"
      |        ^~~~~~~
chip/lpc17_40_allocateheap.c:176:6: warning: #warning "CONFIG_MM_REGIONS > 1: This configuration has no available AHB SRAM Bank0/1" [-Wcpp]
  176 | #    warning "CONFIG_MM_REGIONS > 1: This configuration has no available AHB SRAM Bank0/1"
      |      ^~~~~~~
chip/stm32l4_allocateheap.c:141:4: warning: #warning "CONFIG_MM_REGIONS large enough but I do not know what some of the region(s) are" [-Wcpp]
  141 | #  warning "CONFIG_MM_REGIONS large enough but I do not know what some of the region(s) are"
      |    ^~~~~~~

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>

boards/arm/sam34/sam3u-ek/configs/knsh/defconfig

@@ -27,7 +27,7 @@ CONFIG_FS_FAT=y
 CONFIG_MAX_TASKS=16
 CONFIG_MAX_WDOGPARMS=2
 CONFIG_MMCSD=y
-CONFIG_MM_REGIONS=2
+CONFIG_MM_REGIONS=3
 CONFIG_NFILE_DESCRIPTORS=8
 CONFIG_NFILE_STREAMS=8
 CONFIG_NSH_DISABLE_DD=y

boards/arm/sam34/sam3u-ek/configs/nsh/defconfig

@@ -24,7 +24,7 @@ CONFIG_BUILTIN=y
 CONFIG_FS_FAT=y
 CONFIG_MAX_TASKS=16
 CONFIG_MAX_WDOGPARMS=2
-CONFIG_MM_REGIONS=2
+CONFIG_MM_REGIONS=3
 CONFIG_NFILE_DESCRIPTORS=8
 CONFIG_NFILE_STREAMS=8
 CONFIG_NSH_ARCHINIT=y

boards/arm/sam34/sam3u-ek/configs/nx/defconfig

@@ -40,7 +40,7 @@ CONFIG_LCD_MAXPOWER=31
 CONFIG_LCD_PORTRAIT=y
 CONFIG_MAX_TASKS=16
 CONFIG_MAX_WDOGPARMS=2
-CONFIG_MM_REGIONS=2
+CONFIG_MM_REGIONS=3
 CONFIG_MQ_MAXMSGSIZE=64
 CONFIG_NFILE_DESCRIPTORS=12
 CONFIG_NFILE_STREAMS=12

boards/arm/sam34/sam3u-ek/configs/nxwm/defconfig

@@ -36,7 +36,7 @@ CONFIG_LCD_MAXCONTRAST=1
 CONFIG_LCD_MAXPOWER=31
 CONFIG_MAX_TASKS=16
 CONFIG_MAX_WDOGPARMS=2
-CONFIG_MM_REGIONS=2
+CONFIG_MM_REGIONS=3
 CONFIG_MQ_MAXMSGSIZE=64
 CONFIG_NFILE_DESCRIPTORS=12
 CONFIG_NFILE_STREAMS=12