MSP430: Add input section rules for .upper sections to default linker script

ld/ChangeLog:

2020-01-16  Jozef Lawrynowicz  <jozef.l@mittosystems.com>

	* scripttempl/elf32msp430.sc: Add input section rules for
	.upper.{text,data,rodata,bss}.
	* testsuite/ld-msp430-elf/msp430-elf.exp: Run new test.
	* testsuite/ld-msp430-elf/upper-input-sections.s: New test.