target/mips: fix emulation of nanoMIPS BPOSGE32 instruction

target/mips: fix emulation of nanoMIPS BPOSGE32 instruction

Per the "MIPS® Architecture Extension: nanoMIPS32 DSP Technical
Reference Manual — Revision 0.04" p. 88 "BPOSGE32C", offset argument (imm)
should be left-shifted first.
This change was tested against test_dsp_r1_bposge32.c DSP test.

Reported-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Aleksandar Rikalo <aleksandar.rikalo@syrmia.com>
Signed-off-by: Filip Vidojevic <filip.vidojevic@syrmia.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <VI1PR0302MB34869449EE56F226FC3C21129C309@VI1PR0302MB3486.eurprd03.prod.outlook.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>