arm: Initialize vector costing fields

arm: Initialize vector costing fields

The movi, dup and extract costing fields were recently added to struct
vector_cost_table, but there initialization is missing for the arm
(aarch32) specific descriptions.

Although the arm port does not use these fields (only aarch64 does),
this is causing warnings during the build, and even build failures
when using gcc-4.8.5 as host compiler:

/gccsrc/gcc/config/arm/arm.c:1194:1: error: uninitialized const member 'vector_cost_table::movi'
 };
  ^
/gccsrc/gcc/config/arm/arm.c:1194:1: warning: missing initializer for member 'vector_cost_table::movi' [-Wmissing-field-initializers]
/gccsrc/gcc/config/arm/arm.c:1194:1: error: uninitialized const member 'vector_cost_table::dup'
/gccsrc/gcc/config/arm/arm.c:1194:1: warning: missing initializer for member 'vector_cost_table::dup' [-Wmissing-field-initializers]
/gccsrc/gcc/config/arm/arm.c:1194:1: error: uninitialized const member 'vector_cost_table::extract'
/gccsrc/gcc/config/arm/arm.c:1194:1: warning: missing initializer for member 'vector_cost_table::extract' [-Wmissing-field-initializers]

This patch uses the same initialization values as in aarch64 for
consistency:
+    COSTS_N_INSNS (1),  /* movi.  */
+    COSTS_N_INSNS (2),  /* dup.  */
+    COSTS_N_INSNS (2)   /* extract.  */

2021-11-10  Christophe Lyon  <christophe.lyon@foss.st.com>

	gcc/
	* config/arm/arm.c (cortexa9_extra_costs, cortexa8_extra_costs,
	cortexa5_extra_costs, cortexa7_extra_costs,
	cortexa12_extra_costs, cortexa15_extra_costs, v7m_extra_costs):
	Initialize movi, dup and extract costing fields.