targets: remove hifive1-qemu target

This target was added purely for running tests, and it is currently
unused. When I try to use it, it causes runtime exceptions.
The replacement riscv-qemu is much better behaved.

This doesn't drop support for any actual hardware, the HiFive 1 B will
remain supported.

targets/hifive1-qemu.json

@@ -1,8 +0,0 @@
-{
-	"inherits": ["fe310"],
-	"build-tags": ["hifive1b", "qemu"],
-	"serial": "uart",
-	"default-stack-size": 4096,
-	"linkerscript": "targets/hifive1-qemu.ld",
-	"emulator": "qemu-system-riscv32 -machine sifive_e -nographic -kernel {}"
-}

targets/hifive1-qemu.ld

@@ -1,16 +0,0 @@
-
-/* memory map:
- * https://github.com/sifive/freedom-e-sdk/blob/v201908-branch/bsp/sifive-hifive1/metal.default.lds
- * With one change: this linkerscript uses 64K RAM instead of 16K as specified
- * in metal.default.lds. Not sure why this works, but it works, and it avoids
- * out-of-memory issues when running tests.
- */
-MEMORY
-{
-    FLASH_TEXT (rw) : ORIGIN = 0x20400000, LENGTH = 0x1fc00000
-    RAM (xrw)       : ORIGIN = 0x80000000, LENGTH = 64K
-}
-
-_stack_size = 2K;
-
-INCLUDE "targets/riscv.ld"