ARM: 8340/1: ARMv7-M: Enlarge vector table up to 256 entries

From Cortex-M reference manuals, the nvic supports up to 240 interrupts.
So the number of entries in vectors table is up to 256.

This patch adds a new config flag to specify the number of external interrupts.
Some ifdeferies are added in order to respect the natural alignment without
wasting too much space on smaller systems.

Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Stefan Agner <stefan@agner.ch>
Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mm/Kconfig

@@ -604,6 +604,21 @@ config CPU_USE_DOMAINS
 	  This option enables or disables the use of domain switching
 	  via the set_fs() function.
 
+config CPU_V7M_NUM_IRQ
+	int "Number of external interrupts connected to the NVIC"
+	depends on CPU_V7M
+	default 90 if ARCH_STM32
+	default 38 if ARCH_EFM32
+	default 240
+	help
+	  This option indicates the number of interrupts connected to the NVIC.
+	  The value can be larger than the real number of interrupts supported
+	  by the system, but must not be lower.
+	  The default value is 240, corresponding to the maximum number of
+	  interrupts supported by the NVIC on Cortex-M family.
+
+	  If unsure, keep default value.
+
 #
 # CPU supports 36-bit I/O
 #